Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss, Net [Member]
Balance at Dec. 31, 2013	$ 7,787	$ 2	$ 0	$ 4,479	$ 3,315	$ (9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	578				578
Common stock dividends declared	(725)				(725)
Balance at Sep. 30, 2014	7,640	2	0	4,479	3,168	(9)
Balance at Dec. 31, 2014	7,756	2	0	4,479	3,288	(13)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	550				550
Common stock dividends declared	(950)				(950)
Balance at Sep. 30, 2015	$ 7,356	$ 2	$ 0	$ 4,479	$ 2,888	$ (13)