Impairment of Long-lived Assets - Components of Net Investment in Long-term Leases (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Oct. 31, 2000
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Estimated residual value of leased assets	$ 639	$ 685	$ 1,600
Less: unearned income	287	324
Net investment in long-term leases	$ 352	$ 361