Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
U.S. federal income taxes:
Current	$ 503	$ 413	$ 410
Deferred	8	121	84
Provision for federal income taxes	511	534	494
Foreign income taxes:
Current	310	163	153
Deferred	(11)	66	35
Benefit of net operating loss carryforwards	(48)	(13)	(13)
Provision for foreign income taxes	251	216	175
State income taxes:
Current	66	50	64
Deferred	(8)	9	(16)
Provision for state income taxes	58	59	48
Provision for income taxes	$ 820	$ 809	$ 717