Income Tax (Provision for Income Tax from Continuing Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ (246)	$ 520	$ 632
State and local	5	3	10
Foreign	891	628	556
Subtotal	650	1,151	1,198
Deferred:
Federal	(2,373)	(827)	194
Foreign	253	369	198
Subtotal	(2,120)	(458)	392
Current and Deferred:
Provision for income tax expense (benefit)	$ (1,470)	$ 693	$ 1,590