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	339				339
Common stock dividends declared	(625)				(625)
Balance at Jun. 30, 2014	7,501	2	0	4,479	3,029	(9)
Balance at Dec. 31, 2014	7,756	2	0	4,479	3,288	(13)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	305				305
Common stock dividends declared	(700)				(700)
Balance at Jun. 30, 2015	$ 7,361	$ 2	$ 0	$ 4,479	$ 2,893	$ (13)