Parent Company Financial Statements (Parent Company Condensed Statements of Cash Flows) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows From Operating Activities:
Net income	$ 2,226	$ 1,729	$ 2,028
Net change in other assets	280	92	(210)
Net change in accounts payable and accrued liabilities	(4)	(812)	346
Other, net	67	(5)	(161)
Net cash from operating activities	3,258	5,339	3,714
Cash Flows From Investing Activities:
Purchases of AFS securities	(3,685)	(6,463)	(7,026)
Proceeds from maturities, calls and paydowns of HTM securities	1,866	2,863	5,536
Net cash from business combinations	1,025	(6)	675
Net cash from divestitures	0	522	0
Net cash from investing activities	(4,063)	(4,240)	(7,047)
Cash Flows From Financing Activities:
Net change in long-term debt	5,510	4,164	2,327
Net change in short-term borrowings	(421)	1,274	(702)
Net proceeds from preferred stock transactions	0	487	2,116
Other, net	265	248	55
Net cash from financing activities	965	(1,973)	2,796
Net Change in Cash and Cash Equivalents	160	(874)	(537)
Cash and Cash Equivalents at Beginning of Period	2,165	3,039	3,576
Cash and Cash Equivalents at End of Period	2,325	2,165	3,039
Parent Company [Member]
Cash Flows From Operating Activities:
Net income	2,226	1,729	2,028
Equity in earnings of subsidiaries in excess of dividends from subsidiaries	(605)	(616)	(418)
Net change in other assets	27	95	265
Net change in accounts payable and accrued liabilities	40	42	(71)
Other, net	(86)	(79)	(228)
Net cash from operating activities	1,602	1,171	1,576
Cash Flows From Investing Activities:
Proceeds from sales, calls and maturities of AFS securities	25	24	26
Purchases of AFS securities	(124)	(24)	(26)
Proceeds from maturities, calls and paydowns of HTM securities	16	2	4
Investment in subsidiaries	(1)	(4)	(30)
Advances to subsidiaries	(7,145)	(5,815)	(10,785)
Proceeds from repayment of advances to subsidiaries	7,060	5,898	11,325
Net cash from business combinations	0	0	51
Net cash from divestitures	0	9	0
Net cash from investing activities	(169)	90	565
Cash Flows From Financing Activities:
Net change in long-term debt	1,085	499	(2,764)
Net change in short-term borrowings	(24)	(13)	(259)
Net change in advances from subsidiaries	(10)	50	(72)
Net proceeds from common stock issued	294	108	15
Net proceeds from preferred stock transactions	0	487	2,116
Cash dividends paid on common and preferred stock	(814)	(912)	(564)
Other, net	0	8	62
Net cash from financing activities	531	227	(1,466)
Net Change in Cash and Cash Equivalents	1,964	1,488	675
Cash and Cash Equivalents at Beginning of Period	5,727	4,239	3,564
Cash and Cash Equivalents at End of Period	$ 7,691	$ 5,727	$ 4,239