Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net income	$ 279,328	$ 277,977	$ 237,866
Adjustments to reconcile net income to net cash from operating activities:
Provision for loan losses	51,845	16,314	20,582
Deferred tax expense (benefit)	(19,059)	(4,130)	3,279
Accretion of loan discounts	(14,447)	(14,567)	(12,654)
Securities premium amortization (discount accretion), net	73,785	61,268	41,921
Net (gain) loss on securities transactions	(69)	(38)	(1,176)
Depreciation and amortization	41,960	39,694	38,471
Net (gain) loss on sale/write-down of assets/foreclosed assets	(1,765)	761	3,235
Stock-based compensation	12,737	12,503	11,963
Net tax benefit (deficiency) from stock-based compensation	45	19	(393)
Excess tax benefits from stock-based compensation	(1,389)	(3,183)	(2,686)
Earnings on life insurance policies	(3,585)	(3,218)	(3,103)
Net change in:
Trading account securities	(1,153)	972	14,686
Accrued interest receivable and other assets	(12,860)	(73,184)	(7,996)
Accrued interest payable and other liabilities	(11,902)	(24,518)	(170,389)
Net cash from operating activities	393,471	286,670	173,606
Investing Activities:
Securities held to maturity: Purchases	(1,350)	0	(257,571)
Securities held to maturity: Maturities, calls and principal repayments	209,425	153,523	14,891
Securities available for sale:
Purchases	(14,147,908)	(19,484,433)	(11,178,144)
Sales	12,683,169	12,151,287	10,056,060
Maturities, calls and principal repayments	658,199	4,987,629	1,311,643
Net change in loans	(500,990)	(800,120)	(317,987)
Net cash received (paid) in acquisitions	0	830,661	(1,896)
Benefits received on life insurance policies	444	0	0
Proceeds from sales of premises and equipment	2,538	49	18,481
Purchases of premises and equipment	(147,129)	(131,970)	(39,599)
Proceeds from sales of repossessed properties	4,682	11,281	8,200
Net cash from investing activities	(1,238,920)	(2,282,093)	(385,922)
Financing Activities:
Net change in deposits	207,665	1,823,101	1,191,420
Net change in short-term borrowings	90,403	84,677	107,192
Principal payments on long-term borrowings	0	0	(7)
Proceeds from stock option exercises	14,853	29,158	68,653
Excess tax benefits from stock-based compensation	1,389	3,183	2,686
Proceeds from issuance of preferred stock	0	0	144,486
Purchase of treasury stock	(101,237)	(1,457)	(144,630)
Cash dividends paid on preferred stock	(8,063)	(8,063)	(6,719)
Cash dividends paid on common stock	(132,161)	(127,178)	(119,619)
Net cash from financing activities	72,849	1,803,421	1,243,462
Net change in cash and cash equivalents	(772,600)	(192,002)	1,031,146
Cash and cash equivalents at beginning of year	4,364,123	4,556,125	3,524,979
Cash and cash equivalents at end of year	$ 3,591,523	$ 4,364,123	$ 4,556,125