Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING ACTIVITIES:
Net income	$ 276,854	$ 266,975	$ 262,784
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	36,318	28,727	29,531
Provision for depreciation and amortization	40,929	42,803	42,303
Amortization of investment security premiums, net	31,493	32,618	23,211
Deferred income tax (benefit) expense	(2,059)	7,432	(540)
Investment securities (gains) losses, net	53	(6,320)	(14,124)
Net gains on sales of loans held for sale	(5,850)	(3,076)	0
Proceeds from sales of loans held for sale	160,875	97,813	0
Origination Of Loans Held For Sale	(163,469)	(103,199)	0
Net (increase) decrease in trading securities	73,780	(86,045)	16,005
Stock-based compensation	11,525	10,147	8,829
(Increase) decrease in interest receivable	(3,642)	(4,992)	(2,185)
Decrease in interest payable	1,107	336	(230)
Increase (decrease) in income taxes payable	4,509	19,165	344
Net tax benefit related to equity compensation plans	(3,390)	(2,132)	(1,850)
Other changes, net	(26,666)	(11,189)	(3,242)
Net cash provided by (used in) operating activities	432,367	289,063	360,836
INVESTING ACTIVITIES
Cash paid in sales of branches	0	0	(43,827)
Proceeds from sales of available for sale securities	24,380	689,031	64,442
Proceeds from maturities/pay downs of available for sale securities	2,032,397	2,515,113	1,914,105
Purchases of available for sale securities	(1,988,101)	(3,542,537)	(2,498,090)
Net (increase) decrease in loans	(1,009,523)	(1,005,657)	(560,890)
Repayments of long-term securities purchased under agreements to resell	(250,000)	0	(450,000)
Proceeds from Securities Purchased under Agreements to Resell	400,000	175,000	550,000
Purchases of land, buildings and equipment	(24,478)	(31,897)	(43,658)
Sales of land, buildings and equipment	10,112	5,545	5,236
Net cash provided by (used in) investing activities	(805,213)	(1,195,402)	(1,062,682)
FINANCING ACTIVITIES
Net increase (decrease) in non-interest bearing, savings, interest checking and money market deposits	782,846	545,147	282,276
Net increase (decrease) in time open and C.D.’s	243,199	(124,509)	(57,956)
Repayment of long-term securities sold under agreements to repurchase	0	0	(350,000)
Net increase (decrease) in short-term federal funds purchased and securities sold under agreements to repurchase	(239,647)	101,034	865,960
Repayment of other long-term borrowings	(1,769)	(240)	(3,252)
Proceeds from issuance of preferred stock	0	0	144,784
Purchases of treasury stock	(39,381)	(23,176)	(70,974)
Accelerated stock repurchase agreement net outflow	0	(100,000)	(200,000)
Issuance of stock under stock purchase and equity compensation plans	(6)	1,914	8,652
Net tax benefit related to equity compensation plans	3,390	2,132	1,850
Cash dividends paid on common stock	(87,070)	(84,961)	(84,241)
Cash dividends paid on preferred stock	(9,000)	(9,000)	(4,050)
Net cash provided by (used in) financing activities	652,562	308,341	533,049
Increase (decrease) in cash and cash equivalents	279,716	(597,998)	(168,797)
Cash and cash equivalents at beginning of year	502,719	1,100,717	1,269,514
Cash and cash equivalents at end of year	782,435	502,719	1,100,717
Supplemental Cash Flow Information:
Income tax payments, net	119,596	95,341	120,172
Interest paid on deposits and borrowings	31,896	27,760	28,218
Loans transferred to foreclosed real estate	1,122	3,778	5,074
Accelerated Share Repurchases, Settlement (Payment) or Receipt	0	60,000	0
Transfer of Portfolio Loans and Leases to Held-for-sale	$ 42,688	$ 0	$ 0