UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Cash Flows [Abstract]
CASH FLOWS FROM OPERATING ACTIVITIES	$ 409,335	$ (85,013)
CASH FLOWS FROM INVESTING ACTIVITIES
Cash received in acquisitions, net		414,342
Purchase of securities available-for-sale	(240,734)	(69,743)
Proceeds from sales of securities available-for-sale	37,884	138,354
Proceeds from maturities, calls and paydowns of securities available-for-sale	113,400	61,512
Purchases of other securities, net	(574)	(15,573)
Proceeds from sales of loans held for sale	46,866	16,984
Increase in loans, net	(436,758)	(229,830)
Purchase of premises and equipment	(2,742)	(3,081)
Proceeds from disposition of foreclosed property	1,182	3,180
Other, net	(1,871)	(1,068)
Net cash (used in) provided by investing activities	(483,347)	315,077
CASH FLOWS FROM FINANCING ACTIVITIES
Decrease in deposits, net	(253,289)	(606,131)
Net change in securities sold under agreements to repurchase		(23,587)
Net change in short term FHLB advances		245,000
Repurchase of common stock	(29,973)	(58,830)
Cash dividends paid on common stock	(22,139)	(22,727)
Net cash used in financing activities	(305,401)	(466,275)
Net decrease in cash and cash equivalents	(379,413)	(236,211)
Cash and cash equivalents at beginning of period	988,764	779,280
Cash and cash equivalents at end of period	609,351	543,069
Cash paid during the period for:
Interest	39,487	44,999
Income taxes (refunded) paid	(234)	81
Cash paid for amounts included in lease liabilities	2,767	2,872
Non-cash investing activities (at fair value):
Acquisition of real estate and other assets in settlement of loans	11,162	599
Transfers of loans held for sale to loans	10,500	17,678
Transfers of loans to loans held for sale		17,444
Securities sold, net, with settlement after quarter end	57,157
Right-of-use assets (remeasured) obtained in exchange for operating lease liabilities	$ (125)	$ 81,601