Commitments and Other Contingencies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Total rent expense incurred under operating leases	$ 324	$ 426	$ 536
Loss Contingencies [Line Items]
Recorded Unconditional Purchase Obligation	155
Other Current Liabilities [Member]
Loss Contingencies [Line Items]
Recorded Unconditional Purchase Obligation	34
Other Noncurrent Liabilities [Member]
Loss Contingencies [Line Items]
Recorded Unconditional Purchase Obligation	121
Other Noncurrent Liabilities [Member] | Fair Value Guarantee [Member]
Loss Contingencies [Line Items]
Leveraged Leases, Net Investment in Leveraged Leases Disclosure, Residual Value of Leased Assets	$ 28