Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Preferred shares	Common Shares	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2012	$ 18,886	$ 0	$ 221	$ 12,067	$ (927)	$ 7,525
Net income	5,359					5,359
Other comprehensive (loss) income	(499)				(499)
Repurchase of common shares	(4,000)		(11)	(648)		(3,341)
Cash dividends declared
Cash dividends declared common, per share	(967)					(967)
Ending Balance at Dec. 31, 2013	19,496	0	213	12,202	(1,426)	8,507
Other changes, primarily employee plans	717		3	783		(69)
Net income	5,885					5,885
Other comprehensive (loss) income	(493)				(493)
Repurchase of common shares	(4,378)		(10)	(604)		(3,764)
Cash dividends declared
Cash dividends declared common, per share	(1,055)					(1,055)
Ending Balance at Dec. 31, 2014	20,673	0	205	12,874	(1,919)	9,513
Other changes, primarily employee plans	476		2	534		(60)
Preferred shares issued	0			742
Net income	5,163					5,163
Other comprehensive (loss) income	(615)				(615)
Repurchase of common shares	(4,509)		(12)	(714)		(3,783)
Cash dividends declared preferred	(62)					(62)
Cash dividends declared
Cash dividends declared common, per share	(1,128)					(1,128)
Ending Balance at Dec. 31, 2015	20,673	$ 0	194	13,348	$ (2,534)	9,665
Other changes, primarily employee plans	310		$ 1	347		$ (38)
Preferred shares issued	$ 0			$ 841