Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 161,907	$ 168,146	$ 102,957
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	24,845	24,431	21,082
Stock-based compensation	12,204	10,032	7,575
Provision for credit losses	9,942	11,869	8,101
Net amortization of premiums and accretion of discounts on securities and borrowings	46,346	24,310	22,080
Amortization of other intangible assets	10,016	11,327	9,169
Losses (gains) on securities transactions, net	20	(777)	(2,487)
Proceeds from sales of loans held for sale	813,855	572,439	144,790
Gains on sales of loans, net	(20,814)	(22,030)	(4,245)
Originations of loans held for sale	(444,290)	(425,713)	(134,328)
Losses (gains) on sales of assets, net	95	(1,358)	(2,776)
Net deferred income tax expense	76,848	27,154	16,453
Net change in:
Trading securities	0	0	14,233
Fair value of borrowings hedged by derivative transactions	0	6,158	1,473
Cash surrender value of bank owned life insurance	(7,338)	(6,694)	(6,815)
Accrued interest receivable	(7,174)	(3,262)	(2,480)
Other assets	(57,353)	47,458	(71,263)
Accrued expenses and other liabilities	121	(24,313)	31,410
Net cash provided by operating activities	619,230	419,177	154,929
Cash flows from investing activities:
Net loan originations and purchases	(1,418,073)	(1,379,431)	(1,754,689)
Investment securities held to maturity:
Purchases	(220,356)	(669,157)	(239,608)
Sales	0	0	11,666
Maturities, calls and principal repayments	290,929	325,766	402,485
Investment securities available for sale:
Purchases	(411,788)	(679,530)	(594,327)
Sales	2,727	4,782	140,640
Maturities, calls and principal repayments	204,684	867,998	142,588
Death benefit proceeds from bank owned life insurance	13,089	2,406	0
Proceeds from sales of real estate property and equipment	9,357	20,560	23,861
Purchases of real estate property and equipment	(18,117)	(20,707)	(34,040)
Cash and cash equivalents acquired in acquisitions	0	0	201,025
Net cash used in investing activities	(1,547,548)	(1,527,313)	(1,700,399)
Cash flows from financing activities:
Net change in deposits	422,754	1,477,157	1,051,660
Net change in short-term borrowings	(332,332)	3,969	873,123
Proceeds from issuance of long-term borrowings, net	1,065,000	385,000	162,792
Repayments of long-term borrowings	(185,000)	(769,182)	(970,000)
Proceeds from issuance of preferred stock, net	98,101	0	111,590
Cash dividends paid to preferred shareholders	(6,277)	(7,188)	(3,813)
Cash dividends paid to common shareholders	(115,881)	(111,813)	(102,279)
Purchase of common shares to treasury	(2,645)	(3,191)	(2,108)
Common stock issued, net	8,207	112,085	7,898
Net cash provided by financing activities	951,927	1,086,837	1,128,863
Net change in cash and cash equivalents	23,609	(21,299)	(416,607)
Cash and cash equivalents at beginning of year	392,501	413,800	830,407
Cash and cash equivalents at end of year	416,110	392,501	413,800
Supplemental disclosures of cash flow information:
Interest on deposits and borrowings	170,614	151,209	159,170
Federal and state income taxes	29,013	26,564	50,027
Supplemental schedule of non-cash investing activities:
Transfer of loans to other real estate owned	7,301	8,089	8,828
Loans transferred to loans held for sale	313,201	174,501	0
Non-cash assets acquired:
Investment securities available for sale	0	0	327,152
Loans	0	0	822,716
Premises and equipment	0	0	8,550
Bank owned life insurance	0	0	5,090
Accrued interest receivable	0	0	3,741
Goodwill	0	0	113,587
Other intangible assets	0	0	18,616
Other assets	0	0	49,831
Total non-cash assets acquired	0	0	1,349,283
Liabilities assumed:
Deposits	0	0	1,167,725
Short-term borrowings	0	0	57,087
Long-term borrowings	0	0	90,738
Accrued expenses and other liabilities	0	0	5,156
Total liabilities assumed	0	0	1,320,706
Net non-cash assets acquired	0	0	28,577
Net cash and cash equivalents acquired in acquisition	0	0	201,025
Common stock issued in acquisition	$ 0	$ 0	$ 229,602