Revenue Recognition:
Truck, Parts and Other: Substantially all sales and revenues of trucks and related aftermarket parts are recorded by the Company when products are shipped to dealers or customers, except for certain truck shipments that are subject to a residual value guarantee to the customer. Revenues related to these shipments are generally recognized on a straight-line basis over the guarantee period (see Note E). At the time certain truck and parts sales to a dealer are recognized, the Company records an estimate of any future sales incentive costs related to such sales. The estimate is based on historical data and announced incentive programs. In the Truck and Parts segments, the Company grants extended payment terms on selected receivables. Interest is charged for the period beyond standard payment terms. Interest income is recorded as earned.
Financial Services: Interest income from finance and other receivables is recognized using the interest method. Certain loan origination costs are deferred and amortized to interest income over the expected life of the contracts, generally 36 to 60 months, using the straight-line method which approximates the interest method. For operating leases, rental revenue is recognized on a straight-line basis over the lease term. Rental revenues for the years ended December 31, 2013, 2012 and 2011 were $631.7, $551.5 and $527.8, respectively. Depreciation and related leased unit operating expenses were $503.5, $434.9 and $412.5 for the years ended December 31, 2013, 2012 and 2011, respectively.
Recognition of interest income and rental revenue is suspended (put on non-accrual status) when the receivable becomes more than 90 days past the contractual due date or earlier if some other event causes the Company to determine that collection is not probable. Accordingly, no finance receivables more than 90 days past due were accruing interest at December 31, 2013 or December 31, 2012. Recognition is resumed if the receivable becomes current by the payment of all amounts due under the terms of the existing contract and collection of remaining amounts is considered probable (if not contractually modified) or if the customer makes scheduled payments for three months and collection of remaining amounts is considered probable (if contractually modified). Payments received while the finance receivable is on non-accrual status are applied to interest and principal in accordance with the contractual terms.