Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating Activities
Net income	$ 21,384	$ 41,444	$ 100,193	$ 77,491
Adjustments reconciling net income to net cash provided by (used in) operating activities:
Depreciation			9,077	7,359
Net losses on sale or disposal of premises and equipment including write-downs			159	78
Net write-downs on other assets			4,359	0
Provision for loan losses	5,989	2,095	14,065	13,006	$ 16,667
Net losses on sale of other real estate owned including write-downs			158	947
Share-based compensation expense			2,450	5,433
Amortization of intangible assets	5,719	2,676	11,972	5,862
Amortization of operating lease right-of-use assets			7,145	0
Provision for deferred taxes			12,084	1,023
Net amortization of investment securities available for sale			3,069	3,909
Net (gain) loss on securities	(4)	(48)	(139)	38
Accretion of discount on purchased loans			(10,503)	(8,083)
Amortization of premium on purchased loan pools			977	1,473
Accretion on other borrowings			33	98
Accretion on subordinated deferrable interest debentures			1,170	1,001
Originations of mortgage loans held for sale			(2,376,070)	(1,361,509)
Payments received on mortgage loans held for sale			4,438	840
Proceeds from sales of mortgage loans held for sale			1,660,599	1,188,493
Net gains on sale of mortgage loans held for sale			(52,605)	(28,236)
Originations of SBA loans			(22,121)	(18,032)
Proceeds from sales of SBA loans			42,647	27,275
Net gains on sale of SBA loans			(4,220)	(2,246)
Increase in cash surrender value of bank owned life insurance			(1,861)	(1,311)
Gain on bank owned life insurance proceeds			(4,335)	0
Loss on sale of loans			1,954	0
Changes in FDIC loss-share payable, net of cash payments			3,695	1,823
Change attributable to other operating activities			4,307	(10,268)
Net cash used in operating activities			(587,303)	(93,536)
Investing Activities, net of effects of business combinations
Proceeds from maturities of time deposits in other banks			10,313	0
Purchases of securities available for sale			(219,352)	(234,711)
Proceeds from prepayments and maturities of securities available for sale			176,760	112,119
Proceeds from sales of securities available for sale			64,995	68,727
Net (increase) decrease in other investments			(44,936)	12,040
Net increase in loans, excluding purchased loans			(1,571,033)	(437,513)
Payments received on purchased loans			619,024	208,910
Payments received on purchased loan pools			32,516	60,042
Purchases of premises and equipment			(5,924)	(7,335)
Proceeds from sales of premises and equipment			5,330	576
Proceeds from sales of other real estate owned			7,448	7,461
Payments paid to FDIC under loss-share agreements			(3,692)	(1,205)
Proceeds from bank owned life insurance			8,178	0
Proceeds from sales of loans			96,162	0
Net cash and cash equivalents received in acquisitions			244,181	51,495
Net cash used in investing activities			(580,030)	(159,394)
Financing Activities, net of effects of business combinations
Net (decrease) increase in deposits			(33,042)	389,884
Net decrease in securities sold under agreements to repurchase			(24,985)	(16,567)
Proceeds from other borrowings			2,969,000	1,530,000
Repayment of other borrowings			(1,921,267)	(1,338,917)
Proceeds from exercise of stock options			3,587	846
Dividends paid - common stock			(14,237)	(11,655)
Purchase of treasury shares			(11,561)	(2,062)
Net cash provided by financing activities			967,495	551,529
Net (decrease) increase in cash and cash equivalents			(199,838)	298,599
Cash and cash equivalents at beginning of period			679,527	330,658	330,658
Cash and cash equivalents at end of period	$ 479,689	$ 629,257	479,689	629,257	$ 679,527
Cash paid during the period for:
Interest			87,066	45,535
Income taxes			32,096	10,252
Loans (excluding purchased loans) transferred to other real estate owned			503	3,764
Purchased loans transferred to other real estate owned			3,908	2,434
Loans transferred from loans held for sale to loans held for investment			0	10,817
Loans transferred from loans held for investment to loans held for sale			1,554	8,831
Loans provided for the sales of other real estate owned			144	53
Initial recognition of operating lease right-of-use assets			27,286	0
Initial recognition of operating lease liabilities			29,651	0
Right-of-use assets obtained in exchange for new operating lease liabilities			262	0
Assets acquired in business acquisitions			5,186,974	3,059,856
Liabilities assumed in business acquisitions			4,317,661	2,410,453
Issuance of common stock in acquisitions			869,294	547,127
Change in unrealized gain (loss) on securities available for sale, net of tax			20,778	(15,590)
Change in unrealized gain (loss) on cash flow hedge, net of tax			$ (470)	$ 294