Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 178,040	$ 226,339	$ 208,393
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	76,920	32,825	46,907
Depreciation and amortization of premises and equipment	28,803	28,200	28,156
Amortization of TCI	30,800	32,810	38,606
Net amortization of investment securities premiums	12,222	9,387	9,297
Deferred income tax benefit	(21,591)	(165)	(15,749)
Re-measurement of net DTA	0	0	(809)
Investment securities gains, net	(3,053)	(4,733)	(37)
Gain on sales of mortgage loans held for sale	(53,599)	(17,882)	(13,021)
Proceeds from sales of mortgage loans held for sale	1,536,174	916,725	795,756
Originations of mortgage loans held for sale	(1,528,633)	(909,572)	(778,304)
Intangible amortization	529	1,427	0
Amortization of issuance costs and discounts on long-term borrowings	1,128	842	813
Stock-based compensation	7,529	7,413	7,965
Other changes, net	(110,781)	(195,903)	(31,153)
Total adjustments	(23,552)	(98,626)	88,427
Net cash provided by operating activities	154,488	127,713	296,820
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of AFS securities	215,150	710,739	54,638
Proceeds from principal repayments and maturities of AFS securities	430,845	234,702	290,681
Proceeds from principal repayments and maturities of HTM securities	93,823	83,121	35,900
Purchase of AFS securities	(1,134,380)	(1,138,070)	(558,949)
Sale (purchase) of FRB and FHLB stock	5,293	(18,139)	(18,522)
Net increase in loans	(2,072,831)	(708,048)	(447,849)
Net purchases of premises and equipment	(20,237)	(33,717)	(39,883)
Net cash paid for acquisition	(1,884)	(5,174)	0
Net change in tax credit investments	(15,259)	(18,760)	(56,733)
Net cash used in investing activities	(2,499,480)	(893,346)	(740,717)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in demand and savings deposits	3,951,905	849,437	435,872
Net increase in time deposits	(506,611)	168,317	142,755
Increase in short-term borrowings	(253,175)	128,464	137,253
Proceeds from long-term borrowings	495,898	485,000	50,000
Repayments of long-term debt	(82,533)	(596,056)	(100,165)
Net proceeds from issuance of preferred stock	192,878	0	0
Net proceeds from issuance of common stock	7,375	6,362	6,735
Dividends paid	(90,957)	(92,330)	(89,654)
Acquisition of treasury stock	(39,748)	(111,457)	(95,308)
Net cash provided by financing activities	3,675,033	837,737	487,488
Net Increase in Cash and Cash Equivalents	1,330,041	72,104	43,591
Cash and Cash Equivalents at Beginning of Year	517,791	445,687	402,096
Cash and Cash Equivalents at End of Year	1,847,832	517,791	445,687
Cash paid during period for:
Interest	112,140	178,612	126,846
Income taxes	16,190	9,193	13,547
Supplemental schedule of certain noncash activities
Transfer of available for sale securities to held to maturity securities	0	0	641,672
Transfer of available for sale securities to held to maturity securities	$ 0	$ 158,898	$ 0