Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OPERATING ACTIVITIES
Net income	$ 521	$ 393	$ 277
Income from discontinued operations, net of tax	0	0	17
Income from continuing operations, net of tax	521	393	260
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	79	144	478
Provision (benefit) for deferred income taxes	158	79	(202)
Depreciation and amortization	133	122	124
Net periodic defined benefit cost	81	53	37
Share-based compensation expense	37	37	32
Net amortization of securities	48	39	26
Accretion of loan purchase discount	(71)	(53)	0
Net securities gains	(12)	(14)	(3)
Excess tax benefits from share-based compensation arrangements	(1)	(1)	(1)
Net change in trading securities	1	3	(10)
Net change in accrued income receivable	5	(8)	15
Net change in accrued expenses payable	35	59	57
Other, net	(260)	49	456
Net cash provided by operating activities	754	902	1,286
INVESTING ACTIVITIES
Maturities and redemptions of investment securities available-for-sale	3,839	2,779	2,152
Sales of investment securities available-for-sale	0	784	151
Purchases of investment securities available-for-sale	(4,032)	(4,453)	(2,410)
Net change in loans	(3,498)	(695)	1,259
Cash and cash equivalents acquired in acquisition of Sterling Bancshares, Inc.	0	721	0
Sales of Federal Home Loan Bank stock	3	36	144
Purchase of Federal Reserve Bank stock	0	(26)	0
Proceeds from sales of indirect private equity and venture capital funds	1	33	0
Other, net	(51)	(134)	(90)
Net cash (used in) provided by investing activities	(3,738)	(955)	1,206
FINANCING ACTIVITIES
Net change in deposits	4,520	3,296	771
Net change in short-term borrowings	40	(82)	(332)
Maturities and redemptions of medium- and long-term debt	(193)	(1,517)	(5,290)
Issuances of medium and long-term debt	0	0	298
Repurchases of common stock	(308)	(116)	(4)
Cash dividends paid on common stock	(97)	(73)	(34)
Issuances of common stock	0	0	849
Redemption of preferred stock	0	0	(2,250)
Cash dividends paid on preferred stock	0	0	(38)
Excess tax benefits from share-based compensation arrangements	1	1	1
Other, net	(1)	17	3
Net cash provided by (used in) financing activities	3,962	1,526	(6,026)
Net increase (decrease) in cash and cash equivalents	978	1,473	(3,534)
Cash and cash equivalents at beginning of period	3,556	2,083	5,617
Cash and cash equivalents at end of period	4,534	3,556	2,083
Interest paid	135	151	227
Income taxes, tax deposits and tax-related interest paid	46	73	108
Noncash investing and financing activities:
Loans transferred to other real estate	42	69	104
Net noncash assets acquired in stock acquisition of Sterling Bancshares, Inc.	$ 0	$ 82	$ 0