UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Cash Flows [Abstract]
NET CASH FLOWS FROM OPERATING ACTIVITIES	$ (85,013)	$ 72,788
CASH FLOWS FROM INVESTING ACTIVITIES
Cash received in acquisition	414,342
Purchase of securities available-for-sale	(69,743)	(111,422)
Proceeds from sales of securities available-for-sale	138,354	64,536
Proceeds from maturities, calls and paydowns of securities available-for-sale	61,512	26,982
Purchases of other securities, net	(15,573)
Proceeds from sale of commercial loans held for sale	16,984	3,500
Increase in loans, net	(229,830)	(397,496)
Purchase of premises and equipment	(3,081)	(2,347)
Proceeds from disposition of foreclosed property	3,180	2,529
Other, net	(1,066)	(460)
Net cash provided by (used in) investing activities	315,079	(414,178)
CASH FLOWS FROM FINANCING ACTIVITIES
(Decrease) increase in deposits, net	(606,131)	37,456
Net change in securities sold under agreements to repurchase	(23,587)	272
Net change in FHLB advances	245,000
Repurchase of common stock	(58,830)
Cash dividends paid on common stock	(22,727)	(10,453)
Net cash (used in) provided by financing activities	(466,275)	27,275
Net decrease in cash and cash equivalents	(236,211)	(314,115)
Cash and cash equivalents at beginning of period	779,280	730,811
Cash and cash equivalents at end of period	$ 543,069	$ 416,696