Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 226,339	$ 208,393	$ 171,753
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	32,825	46,907	23,305
Depreciation and amortization of premises and equipment	28,200	28,156	28,096
Amortization of tax credit investments	32,810	38,606	37,185
Net amortization of investment security premiums	9,387	9,297	10,107
Deferred income tax (benefit) expense	(165)	(15,749)	24,896
Re-measurement of net deferred tax asset	0	(809)	15,635
Investment securities gains, net	(4,733)	(37)	(9,071)
Gain on sales of mortgage loans held for sale	(17,882)	(13,021)	(13,036)
Proceeds from sales of mortgage loans held for sale	916,725	795,756	644,400
Originations of mortgage loans held for sale	(909,572)	(778,304)	(634,197)
Intangible amortization	1,427	0	0
Amortization of issuance costs and discounts on long-term debt	842	813	845
Stock-based compensation	7,413	7,965	5,209
Other changes, net	(195,903)	(31,153)	(17,369)
Total adjustments	(98,626)	88,427	116,005
Net cash provided by operating activities	127,713	296,820	287,758
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of available for sale securities	710,739	54,638	184,734
Proceeds from paydowns and maturities of held to maturity securities	83,121	35,900	0
Proceeds from principal repayments and maturities of available for sale securities	234,702	290,681	417,673
Purchases of securities available for sale	(1,138,070)	(558,949)	(584,921)
Purchase of Federal Reserve Bank and Federal Home Loan Bank stock	(18,139)	(18,522)	(3,272)
Net increase in loans and leases	(708,048)	(447,849)	(1,087,521)
Net purchases of premises and equipment	(33,717)	(39,883)	(33,092)
Net cash paid for acquisitions	(5,174)	0	0
Net change in tax credit investments	(18,760)	(56,733)	(28,932)
Net cash used in investing activities	(893,346)	(740,717)	(1,135,331)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in demand and savings deposits	849,437	435,872	782,525
Net increase in time deposits	168,317	142,755	2,143
Increase in short-term borrowings	128,464	137,253	76,207
Additions to long-term debt	485,000	50,000	223,251
Repayments of long-term debt	(596,056)	(100,165)	(115,153)
Net proceeds from issuance of common stock	6,362	6,735	8,538
Dividends paid	(92,330)	(89,654)	(80,368)
Acquisition of treasury stock	(111,457)	(95,308)	0
Net cash provided by financing activities	837,737	487,488	897,143
Net Increase in Cash and Cash Equivalents	72,104	43,591	49,570
Cash and Cash Equivalents at Beginning of Year	445,687	402,096	352,526
Cash and Cash Equivalents at End of Year	517,791	445,687	402,096
Cash paid during period for:
Interest	178,612	126,846	93,817
Income taxes	9,193	13,547	6,537
Supplemental schedule of certain noncash activities
Transfer of available for sale securities to held to maturity securities	0	641,672	0
Transfer of available for sale securities to held to maturity securities	$ 158,898	$ 0	$ 0