Summary of Significant Accounting Policies (Amounts Attributable to Controlling Interests) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Income (Loss) Attributable to Parent [Abstract]
Income (Loss) from Continuing Operations	$ 376	$ 1,001	$ 624	$ 577	$ 433	$ 890	$ 576	$ 755	$ 2,578	$ 2,654	$ 2,538
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interests									7	9	5
Income (Loss) from Continuing Operations Attributable to Parent									2,571	2,645	2,533
Income (Loss) From Discontinued Operations, net of tax	(598)	180	(112)	122	49	45	(29)	112	(408)	177	(649)
Income (Loss) from Discontinued Operations Attributable to Noncontrolling Interest, net of tax									11	6	1
(Loss) Income from Discontinued Operations Attributable to Parent, net of tax									(419)	171	(650)
Net Income (Loss)	(222)	1,181	512	699	482	935	547	867	2,170	2,831	1,889
Net Income Attributable to Noncontrolling Interest									18	15	6
Net Income (Loss) Attributable to Parent	$ (227)	$ 1,176	$ 509	$ 694	$ 477	$ 932	$ 543	$ 864	$ 2,152	$ 2,816	$ 1,883