Property and equipment
Property and equipment is carried at cost less accumulated depreciation. Included in property and equipment are capitalized costs related to computer software licenses and software developed for internal use. These costs generally consist of certain external payroll and payroll related costs. Certain facilities and equipment held under capital leases are also classified as property and equipment with the related lease obligations recorded as liabilities. Property and equipment depreciation is calculated using the straight-line method over the estimated useful lives of the assets, generally 3 to 10 years for equipment and 40 years for real property. Depreciation expense is reported in operating costs and expenses. Accumulated depreciation on property and equipment was $2.19 billion and $2.41 billion as of December 31, 2013 and 2012, respectively. Depreciation expense on property and equipment was $208 million, $214 million and $222 million in 2013, 2012 and 2011, respectively. The Company reviews its property and equipment for impairment at least annually and whenever events or changes in circumstances indicate that the carrying amount may not be recoverable.