Impairment of Long-lived Assets - Components of the Net Investment in Long-term Leases (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Oct. 31, 2000
Property, Plant and Equipment [Abstract]
Estimated residual value of leased assets	$ 639	$ 685	$ 1,600
Less: unearned income	291	324
Net investment in long-term leases	$ 348	$ 361