Income Taxes, Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Income Taxes [Abstract]
Unrecognized tax benefits	$ 111	$ 169	$ 169	$ 111
Unrecognized tax benefits that would reduce the effective income tax rate				$ 92
Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties [Roll Forward]
Balance at January 1	140	169	155
Additions for tax positions related to the current year	16	14	20
Additions for tax positions related to prior years	2	2	12
Reductions for tax positions related to prior years	(39)	(37)	(11)
Reductions for tax positions related to settlements with taxing authorities	(1)	(1)	(1)
Reduction for tax positions related to prior years as a result of a lapse of statute of limitations	(7)	(7)	(6)
Balance at December 31	$ 111	$ 140	$ 169