Income Taxes (Components of income tax expense and reconciliation of effective tax rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 190	$ 186	$ 13
Foreign	15	10	15
State and local	30	24	14
Current income tax expense	235	220	42
Deferred
Federal	(580)	119	300
Foreign	(2)	(1)	5
State and local	49	5	31
Deferred income tax expense (benefit)	(533)	123	336
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed tax at statutory tax rate	367	318	337
State income taxes, net of federal tax benefit	34	21	41
Non-deductible expenses and other	(3)	9	8
Enactment of the Tax Cuts and Jobs Act	(689)	0	0
Foreign taxes	(7)	(5)	(8)
Total	$ (298)	$ 343	$ 378