Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Activities:
Net income	$ 237,952	$ 217,535	$ 208,764
Adjustments to reconcile net income to net cash from operating activities:
Provision for loan losses	10,080	27,445	43,611
Deferred tax expense (benefit)	(6,405)	8,167	4,644
Accretion of loan discounts	(10,888)	(12,974)	(11,336)
Securities premium amortization (discount accretion), net	21,701	11,441	8,065
Net (gain) loss on securities transactions	(4,314)	(6,414)	(6)
Depreciation and amortization	37,776	37,628	37,588
Net (gain) loss on sale of loans held for sale and other assets	4,603	4,677	5,929
Stock-based compensation	12,836	15,963	14,925
Net tax benefit (deficiency) from stock-based compensation	(555)	(106)	(264)
Excess tax benefits from stock-based compensation	(171)	(422)	(683)
Earnings on life insurance policies	(4,038)	(4,045)	(4,517)
Net change in:
Trading account securities	(16,465)	1,492	1,025
Student loans held for sale			24,029
Accrued interest receivable and other assets	48,176	(15,502)	69,830
Accrued interest payable and other liabilities	(30,289)	(10,516)	22,929
Net cash from operating activities	299,999	274,369	424,533
Investing Activities:
Securities held to maturity: Purchases	(237,503)	(83,184)	(277,998)
Securities held to maturity: Maturities, calls and principal repayments	2,100	665	708
Securities available for sale:
Purchases	(18,328,058)	(8,752,573)	(11,194,766)
Sales	16,587,482	5,587,391	9,997,994
Maturities, calls and principal repayments	1,073,122	729,678	893,702
Net change in loans	(1,241,422)	70,200	176,599
Net cash paid in acquisitions	(7,199)	(650)
Proceeds from sales of premises and equipment	5,085	1,339	1,063
Purchases of premises and equipment	(24,891)	(26,719)	(16,826)
Proceeds from sales of repossessed properties	15,816	18,562	19,705
Net cash from investing activities	(2,155,468)	(2,455,291)	(399,819)
Financing Activities:
Net change in deposits	2,740,618	2,277,406	1,166,032
Net change in short-term borrowings	(161,141)	246,529	(6,375)
Principal payments on long-term borrowings	(19)	(150,019)	(18,889)
Proceeds from stock option exercises	10,516	7,438	38,807
Excess tax benefits from stock-based compensation	171	422	683
Purchase of treasury stock	(436)	(2,029)	(986)
Common stock/treasury stock sold to the 401(k) stock purchase plan			3,539
Cash dividends paid	(116,853)	(112,210)	(108,027)
Net cash from financing activities	2,472,856	2,267,537	1,074,784
Net change in cash and cash equivalents	617,387	86,615	1,099,498
Cash and cash equivalents at beginning of year	2,907,592	2,820,977	1,721,479
Cash and cash equivalents at end of year	$ 3,524,979	$ 2,907,592	$ 2,820,977