Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows From Operating Activities
Net income	$ 91,984	$ 74,846
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation	11,772	10,406
Amortization of other intangible assets	7,025	5,801
Amortization of tax credit investments	12,574
Net premium amortization on investment securities	7,538	7,529
Accretion income related to acquired loans	(22,312)	(22,157)
Share-based compensation expense	3,606	3,184
Excess tax (benefit) expense on share-based compensation	432	160
Provision for loan losses	2,826	1,702
Net securities (gains) losses	(2,282)	(4,575)
Recognition of deferred gain on sale leaseback transactions	(789)	(1,075)
Net (gains) losses on sales of loans and other assets	1,078	(5,398)
Increase in cash surrender value of company-owned life insurance	(5,035)	(4,266)
Residential real estate loans originated for sale	(240,201)	(179,025)
Proceeds from sales of residential real estate loans	234,736	246,549
(Increase) decrease in interest receivable	2,316	1,551
(Increase) decrease in other real estate owned	5,081	7,475
(Increase) decrease in other assets	16,127	3,707
Increase (decrease) in accrued expenses and other liabilities	(21,669)	(20,504)
Total adjustments	12,823	51,064
Net cash flows provided by (used in) operating activities	104,807	125,910
Cash Flows From Investing Activities
Purchases of investment securities available-for-sale	(235,161)	(414,742)
Purchases of Federal Home Loan Bank/Federal Reserve Bank stock	(16,520)	(8,008)
Proceeds from maturities, prepayments, and calls of investment securities available-for-sale	220,753	252,486
Proceeds from sales of investment securities available-for-sale	131,321	186,277
Proceeds from maturities, prepayments, and calls of investment securities held-to-maturity	35,750	48,204
Proceeds from sales of Federal Home Loan Bank/Federal Reserve Bank stock		9
Proceeds from sales of trading securities	128	127
Proceeds from sale of student loan portfolio	70,674
Net principal collected from (loans made to) loan customers	(219,685)	(199,895)
Proceeds from settlements on company-owned life insurance	3,296	2,347
Proceeds from sale of premises and equipment and other assets	4,708	10,120
Purchases of premises and equipment and other assets	(17,005)	(9,461)
Net cash flows provided by (used in) investing activities	(21,741)	(132,536)
Cash Flows From Financing Activities
Deposits	(9,527)	(59,539)
Federal funds purchased and interbank borrowings	(159,989)	14,026
Securities sold under agreements to repurchase	(37,299)	(68,958)
Other borrowings	1,159	(97)
Payments for maturities of Federal Home Loan Bank advances	(898,801)	(892,298)
Proceeds from Federal Home Loan Bank advances	1,045,000	1,055,000
Cash dividends paid on common stock	(39,588)	(35,219)
Common stock repurchased	(1,749)	(1,852)
Proceeds from exercise of stock options	948	2,597
Common stock issued	222	188
Net cash flows provided by (used in) financing activities	(99,624)	13,848
Net increase (decrease) in cash and cash equivalents	(16,558)	7,222
Cash and cash equivalents at beginning of period	290,432	255,519
Cash and cash equivalents at end of period	273,874	262,741
Supplemental cash flow information:
Total interest paid	40,426	26,534
Total taxes paid (net of refunds)	(819)	$ 3,000
Securities transferred from held-to-maturity to available-for-sale	447,026
Securities transferred from available-for-sale to held-to-maturity	$ 323,990