CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2014		0	546
Beginning balance at Dec. 31, 2014	$ 19,268	$ 0	$ 6	$ 18,676	$ 1,294	$ (336)	$ (372)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(16)				(16)
Dividends to RBS	(39)				(39)
Share-based compensation plans (in shares)			1
Share-based compensation plans	8			29		(21)
Employee stock purchase plan shares purchased	2			2
Total comprehensive income:
Net income	209				209
Other comprehensive income	132						132
Total comprehensive income	341				209		132
Ending balance (in shares) at Mar. 31, 2015		0	547
Ending balance at Mar. 31, 2015	19,564	$ 0	$ 6	18,707	1,448	(357)	(240)
Beginning balance (in shares) at Dec. 31, 2015		0	528
Beginning balance at Dec. 31, 2015	19,646	$ 247	$ 6	18,725	1,913	(858)	(387)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(53)				(53)
Dividend to preferred stockholders	(7)				(7)
Share-based compensation plans (in shares)			1
Share-based compensation plans	2			2		0
Employee stock purchase plan shares purchased	3			3
Total comprehensive income:
Net income	223				223
Other comprehensive income	151						151
Total comprehensive income	374				223		151
Ending balance (in shares) at Mar. 31, 2016		0	529
Ending balance at Mar. 31, 2016	$ 19,965	$ 247	$ 6	$ 18,730	$ 2,076	$ (858)	$ (236)