Income Taxes, Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 178	$ 110	$ 124	$ 183
Unrecognized tax benefits that would reduce the effective income tax rate				$ 150
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	178	110	124
Additions for tax positions related to the current year	13	14	16
Additions for tax positions related to prior years	37	66	2
Reductions for tax positions related to prior years	(20)	(4)	(24)
Reductions for tax positions related to settlements with taxing authorities	(7)	0	(1)
Reduction for tax positions related to prior years as a result of a lapse of statute of limitations	(18)	(8)	(7)
Balance at December 31	$ 183	$ 178	$ 110