Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Activities:
Net income	$ 304,261	$ 279,328	$ 277,977
Adjustments to reconcile net income to net cash from operating activities:
Provision for loan losses	51,673	51,845	16,314
Deferred tax expense (benefit)	(11,598)	(19,059)	(4,130)
Accretion of loan discounts	(15,582)	(14,447)	(14,567)
Securities premium amortization (discount accretion), net	79,705	73,785	61,268
Net (gain) loss on securities transactions	(14,975)	(69)	(38)
Depreciation and amortization	48,177	42,138	39,871
Net (gain) loss on sale/write-down of assets/foreclosed assets	(3,618)	(1,765)	761
Stock-based compensation	11,799	12,737	12,503
Net tax benefit from stock-based compensation	5,063	1,434	3,202
Earnings on life insurance policies	(3,599)	(3,585)	(3,218)
Net change in:
Trading account securities	(124)	(1,153)	972
Accrued interest receivable and other assets	(7,395)	(13,038)	(73,361)
Accrued interest payable and other liabilities	(5,945)	(13,291)	(27,701)
Net cash from operating activities	437,842	394,860	289,853
Investing Activities:
Securities held to maturity: Purchases	0	(1,350)	0
Securities held to maturity: Sales	136,719	0	0
Securities held to maturity: Maturities, calls and principal repayments	228,641	209,425	153,523
Securities available for sale:
Purchases	(16,419,833)	(14,147,908)	(19,484,433)
Sales	14,847,380	12,683,169	12,151,287
Maturities, calls and principal repayments	335,750	658,199	4,987,629
Proceeds from sale of loans	30,470	0	0
Net change in loans	(538,989)	(500,990)	(800,120)
Net cash (paid) received in acquisitions	(492)	0	830,661
Benefits received on life insurance policies	906	444	0
Proceeds from sales of premises and equipment	58,774	2,538	49
Purchases of premises and equipment	(53,648)	(147,129)	(131,970)
Proceeds from sales of repossessed properties	341	4,682	11,281
Net cash from investing activities	(1,373,981)	(1,238,920)	(2,282,093)
Financing Activities:
Net change in deposits	1,467,980	207,665	1,823,101
Net change in short-term borrowings	83,470	90,403	84,677
Proceeds from stock option exercises	78,866	14,853	29,158
Purchase of treasury stock	(1,290)	(101,237)	(1,457)
Cash dividends paid on preferred stock	(8,063)	(8,063)	(8,063)
Cash dividends paid on common stock	(134,902)	(132,161)	(127,178)
Net cash from financing activities	1,486,061	71,460	1,800,238
Net change in cash and cash equivalents	549,922	(772,600)	(192,002)
Cash and cash equivalents at beginning of year	3,591,523	4,364,123	4,556,125
Cash and cash equivalents at end of year	$ 4,141,445	$ 3,591,523	$ 4,364,123