Income Taxes - Components of Current and Long-Term Deferred Income Taxes (Details) - Long-term assets and liabilities [Member] - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals [Abstract]
Employee benefits	$ 761	$ 808
Depreciation and amortization	(1,823)	(1,824)
Other accruals and adjustments	796	717
Deferred Tax Assets, Net, Classification [Abstract]
United States federal income tax loss carryforwards	51	20
United States federal income tax credit carryforward	182	183
United States state and local tax loss carryforwards and tax credit carryforwards	63	63
Other foreign tax loss carryforward	1,715	2,265
Other foreign income tax credit carryforwards	63	70
Valuation allowance for income tax loss and income tax credit carryforwards	(1,728)	(2,315)
Other valuation allowance	(41)	(15)
Deferred tax liabilities, net	$ 39	$ (28)