Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net income	$ 206,340	$ 199,726	$ 179,456
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan and lease losses	49,300	37,250	33,500
Deferred tax (benefit) expense	(15,513)	(5,154)	11,499
Depreciation and amortization	34,678	30,585	36,019
Amortization of earning assets and funding premium/discount, net	54,555	50,758	61,395
Stock-based compensation	10,935	10,223	10,664
Gain on sale, net of write-down, on foreclosed and repossessed assets	(311)	(1,297)	(1,295)
(Gain) loss on sale, net of write-down, on premises and equipment	(244)	(292)	1,287
Impairment loss on securities recognized in earnings	110	1,145	7,277
Gain on the sale of investment securities, net	(609)	(5,499)	(712)
Increase in cash surrender value of life insurance policies	(13,020)	(13,178)	(13,770)
Gain from life insurance policies	(220)	(2,229)	(1,070)
Gain, net on sale of loans held for sale	(7,795)	(4,070)	(16,359)
Proceeds from sale of loans held for sale	452,590	287,132	773,887
Originations of loans held for sale	(449,048)	(296,996)	(687,090)
Net (increase) decrease in accrued interest receivable and other assets	(49,899)	(24,502)	84,077
Net increase (decrease) in accrued expenses and other liabilities	35,336	9,213	(14,812)
Net cash provided by operating activities	307,185	272,815	463,953
Investing Activities:
Net (increase) decrease in interest-bearing deposits	(23,212)	(109,021)	31,761
Purchases of available-for-sale securities	(903,240)	(217,920)	(952,995)
Proceeds from maturities and principal payments of available-for-sale securities	558,301	416,821	741,467
Proceeds from sales of available-for-sale securities	123,270	98,402	57,804
Purchases of held-to-maturity securities	(761,033)	(1,113,958)	(989,397)
Proceeds from maturities and principal payments of held-to-maturity securities	681,124	575,009	717,601
Net proceeds (purchase) of Federal Home Loan Bank stock	4,943	(34,412)	(3,248)
Net increase in loans	(1,813,811)	(1,269,290)	(741,818)
Proceeds from loans not originated for sale	33,644	0	12,771
Purchase of life insurance policies	(50,000)	0	0
Proceeds from life insurance policies	3,912	2,178	1,768
Proceeds from the sale of foreclosed properties and repossessed assets	10,511	8,995	7,745
Proceeds from the sale of premises and equipment	650	3,565	1,304
Purchases of premises and equipment	(36,115)	(30,039)	(21,886)
Acquisition of business, net cash acquired	1,396,414	0	0
Net cash (used for) provided by investing activities	(774,642)	(1,669,670)	(1,137,123)
Financing Activities:
Net increase in deposits	853,921	797,244	323,348
Proceeds from Federal Home Loan Bank advances	13,505,000	10,372,226	4,928,120
Repayments of Federal Home Loan Bank advances	(13,700,279)	(9,565,192)	(4,703,287)
Net (decrease) increase in securities sold under agreements to repurchase and other borrowings	(99,356)	(80,906)	255,502
Issuance of long-term debt	0	150,000	0
Repayment of long-term debt	0	(150,000)	(102,579)
Debt issuance costs	0	(1,349)	0
Dividends paid to common shareholders	(80,964)	(67,431)	(48,952)
Dividends paid to preferred shareholders	(8,711)	(10,556)	(10,803)
Exercise of stock options	3,060	2,221	2,736
Excess tax benefits from stock-based compensation	2,338	1,161	389
Common stock issued	0	435	731
Common stock repurchased	(12,564)	(10,741)	0
Shares acquired related to employee share-based compensation plans	(5,251)	(2,326)	(672)
Common stock warrants repurchased	(23)	(3)	(30)
Net cash (used for) provided by financing activities	457,171	1,434,783	644,503
Net (decrease) increase in cash and due from banks	(10,286)	37,928	(28,667)
Cash and due from banks at beginning of period	261,544	223,616	252,283
Cash and due from banks at end of period	251,258	261,544	223,616
Supplemental disclosure of cash flow information:
Interest paid	95,428	89,942	88,388
Income taxes paid	106,991	102,973	62,926
Noncash investing and financing activities:
Transfer of loans and leases to foreclosed properties and repossessed assets	8,714	5,532	11,750
Transfer of loans from portfolio to loans held for sale	585	0	106
Deposits assumed in business acquisition	1,446,899	0	0
Preferred stock conversion	$ 28,939	$ 0	$ 0