Income Taxes (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrecognized Tax Benefits Rollforward (Table Amounts) [Abstract]
Unrecognized tax benefits at beginning of the year	$ 135	$ 223	$ 210
Additions based on tax positions related to the current year	102	35	52
Additions for tax positions of prior years	110	2	17
Reductions for tax positions of prior years	(44)	(40)	(10)
Settlements with taxing authorities	(20)	(84)	0
Other, net	0	(1)	(46)
Net change in unrecognized tax benefits	148	(88)	13
Unrecognized tax benefits at end of the year	$ 283	$ 135	$ 223