Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities:
Net income	$ 237,866	$ 237,952	$ 217,535
Adjustments to reconcile net income to net cash from operating activities:
Provision for loan losses	20,582	10,080	27,445
Deferred tax expense (benefit)	3,279	(6,405)	8,167
Accretion of loan discounts	(12,654)	(10,888)	(12,974)
Securities premium amortization (discount accretion), net	41,921	21,701	11,441
Net (gain) loss on securities transactions	(1,176)	(4,314)	(6,414)
Depreciation and amortization	38,471	37,776	37,628
Net loss on sale/write-down of assets/foreclosed assets	3,235	4,603	4,677
Stock-based compensation	11,963	12,836	15,963
Net tax deficiency from stock-based compensation	(393)	(555)	(106)
Excess tax benefits from stock-based compensation	(2,686)	(171)	(422)
Earnings on life insurance policies	(3,103)	(4,038)	(4,045)
Net change in:
Trading account securities	14,686	(16,465)	1,492
Accrued interest receivable and other assets	(7,996)	48,176	(15,502)
Accrued interest payable and other liabilities	(170,389)	(30,289)	(10,516)
Net cash from operating activities	173,606	299,999	274,369
Investing Activities:
Securities held to maturity: Purchases	(257,571)	(237,503)	(83,184)
Securities held to maturity: Maturities, calls and principal repayments	14,891	2,100	665
Securities available for sale:
Purchases	(11,178,144)	(18,328,058)	(8,752,573)
Sales	10,056,060	16,587,482	5,587,391
Maturities, calls and principal repayments	1,311,643	1,073,122	729,678
Net change in loans	(317,987)	(1,241,422)	70,200
Net cash paid in acquisitions	(1,896)	(7,199)	(650)
Proceeds from sales of premises and equipment	18,481	5,085	1,339
Purchases of premises and equipment	(39,599)	(24,891)	(26,719)
Proceeds from sales of repossessed properties	8,200	15,816	18,562
Net cash from investing activities	(385,922)	(2,155,468)	(2,455,291)
Financing Activities:
Net change in deposits	1,191,420	2,740,618	2,277,406
Net change in short-term borrowings	107,192	(161,141)	246,529
Principal payments on long-term borrowings	(7)	(19)	(150,019)
Proceeds from stock option exercises	68,653	10,516	7,438
Excess tax benefits from stock-based compensation	2,686	171	422
Proceeds from issuance of preferred stock	144,486	0	0
Purchase of treasury stock	(144,630)	(436)	(2,029)
Cash dividends paid on preferred stock	(6,719)	0	0
Cash dividends paid on common stock	(119,619)	(116,853)	(112,210)
Net cash from financing activities	1,243,462	2,472,856	2,267,537
Net change in cash and cash equivalents	1,031,146	617,387	86,615
Cash and cash equivalents at beginning of year	3,524,979	2,907,592	2,820,977
Cash and cash equivalents at end of year	$ 4,556,125	$ 3,524,979	$ 2,907,592