Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash Flows From Operating Activities
Net income	$ 119,240	$ 91,984
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation	13,171	11,772
Amortization of other intangible assets	8,797	7,025
Amortization of tax credit investments	828	12,574
Net premium amortization on investment securities	6,852	7,538
Accretion income related to acquired loans	(20,257)	(22,312)
Share-based compensation expense	3,746	3,606
Excess tax (benefit) expense on share-based compensation	(1,053)	432
Provision for loan losses	2,046	2,826
Net debt securities (gains) losses	(1,062)	(2,282)
Net (gains) losses on sales of loans and other assets	227	1,078
Increase in cash surrender value of company-owned life insurance	(5,899)	(5,035)
Residential real estate loans originated for sale	(282,134)	(240,201)
Proceeds from sales of residential real estate loans	263,028	234,736
(Increase) decrease in interest receivable	(1,079)	2,316
(Increase) decrease in other assets	12,344	21,208
Increase (decrease) in accrued expenses and other liabilities	(44,002)	(22,458)
Total adjustments	(44,447)	12,823
Net cash flows provided by (used in) operating activities	74,793	104,807
Cash Flows From Investing Activities
Purchases of investment securities available-for-sale	(1,039,861)	(235,161)
Purchases of Federal Home Loan Bank/Federal Reserve Bank stock	(14,439)	(16,520)
Proceeds from maturities, prepayments, and calls of investment securities available-for-sale	335,035	220,753
Proceeds from sales of investment securities available-for-sale	267,632	131,321
Proceeds from maturities, prepayments, and calls of investment securities held-to-maturity	35,958	35,750
Proceeds from sales of Federal Home Loan Bank/Federal Reserve Bank stock	19
Proceeds from sales of equity securities	130	128
Proceeds from sale of student loan portfolio		70,674
Loan originations and payments, net	216,356	(219,685)
Proceeds from company-owned life insurance death benefits	4,374	3,296
Proceeds from sales of premises and equipment and other assets	2,534	4,708
Purchases of premises and equipment and other assets	(24,002)	(17,005)
Net cash flows provided by (used in) investing activities	(216,264)	(21,741)
Cash Flows From Financing Activities
Deposits	13,152	(9,527)
Federal funds purchased and interbank borrowings	139,901	(159,989)
Securities sold under agreements to repurchase	(27,754)	(37,299)
Other borrowings	3,864	1,159
Payments for maturities of Federal Home Loan Bank advances	(325,999)	(898,801)
Proceeds from Federal Home Loan Bank advances	425,000	1,045,000
Cash dividends paid on common stock	(45,288)	(39,588)
Common stock repurchased	(58,142)	(1,749)
Proceeds from exercise of stock options	280	948
Common stock issued	278	222
Net cash flows provided by (used in) financing activities	125,292	(99,624)
Net increase (decrease) in cash and cash equivalents	(16,179)	(16,558)
Cash and cash equivalents at beginning of period	317,165	290,432
Cash and cash equivalents at end of period	300,986	273,874
Supplemental cash flow information:
Total interest paid	66,419	40,426
Total taxes paid (net of refunds)	1,204	(819)
Securities transferred from held-to-maturity to available-for-sale		447,026
Securities transferred from available-for-sale to held-to-maturity		$ 323,990
Operating lease right-of-use assets obtained in exchange for lease obligations	117,751
Finance lease right-of-use assets obtained in exchange for lease obligations	$ 7,871