Supplemental Financial Information - Other Non-Current Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016
Other Liabilities, Noncurrent [Abstract]
Postretirement obligation	$ 274		$ 256
Non-current lease-related obligations	94		125
Permanently grounded aircraft liability noncurrent	18	[1]	0
Other deferred compensation	225		204
Other	81		108
Other noncurrent liabilities	713		728
Other Noncurrent Liabilities
Other Liabilities, Noncurrent [Abstract]
Derivative contracts	$ 21		$ 35

[1] These amounts represent the current and noncurrent portion of the Company's cease-use liability recorded during third quarter 2017, as a result of the Company grounding its remaining leased Boeing 737-300 aircraft on September 29, 2017.