Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provisional net benefit related to U.S. 2017 Tax Reform, estimated impact	$ 151
Estimated write-down of net deferred tax liabilities	$ 334	$ 0	$ 0
U.S. statutory tax rate (as a percent)	35.00%	35.00%	35.00%
U.S. statutory tax rate (as a percent) under U.S. 2017 Tax Reform	21.00%
Estimated cost of a mandatory deemed repatriation of non-U.S. earnings	$ 183	$ 0	$ 0
Resulting tax liability, net of foreign tax credits, estimated cost of a mandatory deemed repatriation of non-U.S. earnings	$ 131
U.S. federal tax cost for mandatory deemed repatriation for non-US earnings held in liquid assets (as a percent)	15.50%
U.S. federal tax cost for mandatory deemed repatriation for non-US earnings held in non-liquid assets (as a percent)	8.00%
Reconciliation of statutory rate to effective income tax rate
Taxes computed at U.S. statutory rates	$ 206	$ 196	$ 217
U.S. statutory tax rate (as a percent)	35.00%	35.00%	35.00%
(Decreases) increases in taxes resulting from:
State Income Tax, net of Federal Tax	$ 2	$ 2	$ 3
State Income Tax, net of Federal Tax (as a percent)	0.30%	0.40%	0.50%
Subsidiaries' results subject to tax rates other than U.S. statutory rates	$ (31)	$ (36)	$ (25)
Subsidiaries' results subject to tax rates other than U.S. statutory rates (as a percent)	(5.30%)	(6.50%)	(4.00%)
Income from non-U.S. subsidiaries taxed at U.S. statutory rates, net of foreign tax credits	$ (16)	$ 2	$ (39)
Income from non-U.S. subsidiaries taxed at U.S. statutory rates, net of foreign tax credits (as a percent)	(2.70%)	0.30%	(6.30%)
Foreign currency translation taxed at non-U.S. subsidiaries	$ (12)	$ 13	$ 6
Foreign currency translation taxed at non-U.S subsidiaries (as a percent)	(2.00%)	2.30%	0.90%
U.S. deferred tax rate change	$ (334)	$ 0	$ 0
U.S. deferrd tax rate change (as a percent)	(56.60%)	0.00%	0.00%
Mandatory deemed repatriation of non-U.S. earnings	$ 183	$ 0	$ 0
Mandatory deemed repatriation of non-U.S. earnings (as a percent)	31.00%	0.00%	0.00%
Other, net	$ (2)	$ (6)	$ (4)
Other, net (as a percent)	(0.40%)	(1.10%)	(0.60%)
Provision (benefit) for income taxes	$ (4)	$ 171	$ 158
Provision (benefit) for income taxes, Effective Income Tax Rate (as a percent)	(0.70%)	30.40%	25.50%