| 1 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due in one year or less, amortized cost | 100000000 | USD | -6 |
| 2 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due in one year or less, amortized cost | 100000000 | USD | -6 |
| 3 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due in one year or less, amortized cost | 100000000 | USD | -6 |
| 4 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due in one year or less, amortized cost | 300000000 | USD | -6 |
| 5 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due after one year through five years, amortized cost | 100000000 | USD | -6 |
| 6 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due after one year through five years, amortized cost | 300000000 | USD | -6 |
| 7 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due after one year through five years, amortized cost | 100000000 | USD | -6 |
| 8 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due after one year through five years, amortized cost | 100000000 | USD | -6 |
| 9 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due after five years through ten years, amortized cost | 100000000 | USD | -6 |
| 10 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due after five years through ten years, amortized cost | 300000000 | USD | -6 |
| 11 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due after five years through ten years, amortized cost | 100000000 | USD | -6 |
| 12 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due after five years through ten years, amortized cost | 100000000 | USD | -6 |
| 13 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due after ten years, amortized cost | 300000000 | USD | -6 |
| 14 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due after ten years, amortized cost | 100000000 | USD | -6 |
| 15 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due after ten years, amortized cost | 100000000 | USD | -6 |
| 16 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due after ten years, amortized cost | 100000000 | USD | -6 |
| 17 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | No contractual maturity dates, amortized cost | 100000000 | USD | -6 |
| 18 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | No contractual maturity dates, amortized cost | 100000000 | USD | -6 |
| 19 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | No contractual maturity dates, amortized cost | 300000000 | USD | -6 |
| 20 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | No contractual maturity dates, amortized cost | 100000000 | USD | -6 |
| 21 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due in one year or less, estimated fair value | 100000000 | USD | -6 |
| 22 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due in one year or less, estimated fair value | 300000000 | USD | -6 |
| 23 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due in one year or less, estimated fair value | 100000000 | USD | -6 |
| 24 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due in one year or less, estimated fair value | 100000000 | USD | -6 |
| 25 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due after one year through five years, estimated fair value | 300000000 | USD | -6 |
| 26 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due after one year through five years, estimated fair value | 100000000 | USD | -6 |
| 27 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due after one year through five years, estimated fair value | 100000000 | USD | -6 |
| 28 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due after one year through five years, estimated fair value | 100000000 | USD | -6 |
| 29 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due after five years through ten years, estimated fair value | 100000000 | USD | -6 |
| 30 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due after five years through ten years, estimated fair value | 100000000 | USD | -6 |
| 31 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due after five years through ten years, estimated fair value | 100000000 | USD | -6 |
| 32 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due after five years through ten years, estimated fair value | 300000000 | USD | -6 |
| 33 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Due after ten years, estimated fair value | 100000000 | USD | -6 |
| 34 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Due after ten years, estimated fair value | 100000000 | USD | -6 |
| 35 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Due after ten years, estimated fair value | 100000000 | USD | -6 |
| 36 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Due after ten years, estimated fair value | 300000000 | USD | -6 |
| 37 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | No contractual maturity dates, estimated fair value | 100000000 | USD | -6 |
| 38 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | No contractual maturity dates, estimated fair value | 100000000 | USD | -6 |
| 39 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | No contractual maturity dates, estimated fair value | 300000000 | USD | -6 |
| 40 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | No contractual maturity dates, estimated fair value | 100000000 | USD | -6 |
| 41 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Available-for-sale securities at estimated fair value | 500000000 | USD | -6 |
| 42 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Available-for-sale securities at estimated fair value | 500000000 | USD | -6 |
| 43 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Available-for-sale securities at estimated fair value | 1500000000 | USD | -6 |
| 44 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Available-for-sale securities at estimated fair value | 500000000 | USD | -6 |
| 45 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | All Available-for-Sale Debt and Equity Securities [Domain] | Available-for-sale securities at amortized cost | 1500000000 | USD | -6 |
| 46 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Treasury bills [Member] | Available-for-sale securities at amortized cost | 500000000 | USD | -6 |
| 47 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Corporate bonds [Member] | Available-for-sale securities at amortized cost | 500000000 | USD | -6 |
| 48 | 0000000001 (https://www.sec.gov/CIK) | 2019-12-31 | Sovereign debt securities [Member] | Available-for-sale securities at amortized cost | 500000000 | USD | -6 |