Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows From Operating Activities
Net income	$ 143,332	$ 114,218
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation	17,666	16,178
Amortization of other intangible assets	10,308	8,442
Amortization of tax credit investments	21,807
Net premium amortization on investment securities	11,290	11,263
Accretion income related to acquired loans	(29,525)	(33,207)
Share-based compensation expense	5,629	4,684
Excess tax (benefit) expense on share-based compensation	416	126
Provision for loan losses	3,576	2,013
Net securities (gains) losses	(2,417)	(7,547)
Recognition of deferred gain on sale leaseback transactions	(1,183)	(1,612)
Net (gains) losses on sales of loans and other assets	(215)	(5,082)
Increase in cash surrender value of company-owned life insurance	(7,993)	(6,288)
Residential real estate loans originated for sale	(377,702)	(336,238)
Proceeds from sales of residential real estate loans	378,849	403,128
(Increase) decrease in interest receivable	5,112	6,039
(Increase) decrease in other real estate owned	5,247	8,287
(Increase) decrease in other assets	700	8,498
Increase (decrease) in accrued expenses and other liabilities	(4,392)	(4,370)
Total adjustments	37,173	74,314
Net cash flows provided by (used in) operating activities	180,505	188,532
Cash Flows From Investing Activities
Purchases of investment securities available-for-sale	(448,567)	(566,089)
Purchases of Federal Home Loan Bank/Federal Reserve Bank stock	(16,520)	(15,647)
Proceeds from maturities, prepayments, and calls of investment securities available-for-sale	316,239	337,766
Proceeds from sales of investment securities available-for-sale	136,648	284,315
Proceeds from maturities, prepayments, and calls of investment securities held-to-maturity	49,520	53,586
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	(211,199)	(356,057)
Proceeds from settlements on company-owned life insurance	6,501	2,347
Proceeds from sales of premises and equipment and other assets	6,013	15,058
Purchases of premises and equipment and other assets	(24,704)	(17,675)
Net cash flows provided by (used in) investing activities	(115,267)	(262,260)
Cash Flows From Financing Activities
Deposits	(7,703)	(136,469)
Federal funds purchased and interbank borrowings	114,998	104,018
Securities sold under agreements to repurchase	(64,979)	(81,643)
Other borrowings	2,427	(116)
Payments for maturities of Federal Home Loan Bank advances	(998,801)	(893,363)
Proceeds from Federal Home Loan Bank advances	945,000	1,130,000
Cash dividends paid on common stock	(59,394)	(52,841)
Common stock repurchased	(1,776)	(1,917)
Proceeds from exercise of stock options	948	2,604
Common stock issued	371	303
Net cash flows provided by (used in) financing activities	(68,909)	70,576
Net increase (decrease) in cash and cash equivalents	(3,671)	(3,152)
Cash and cash equivalents at beginning of period	290,432	255,519
Cash and cash equivalents at end of period	286,761	252,367
Supplemental cash flow information:
Total interest paid	65,880	43,205
Total taxes paid (net of refunds)	1,681	$ 2,958
Securities transferred from held-to-maturity to available-for-sale	447,026
Securities transferred from available-for-sale to held-to-maturity	$ 323,990