Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income	$ 261,988	$ 161,441	$ 121,027
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	15,759	13,120	10,014
Net losses on sale or disposal of premises and equipment	777	41	133
Net write-downs on other assets	1,715	6,210	0
Provision for credit losses	145,380	19,758	16,667
Net write-downs and losses on sale of other real estate owned	1,049	496	1,301
Share-based compensation expense	3,810	3,424	6,241
Amortization of intangible assets	19,612	17,713	9,512
Amortization of operating lease right of use assets	19,740	10,264	0
Provision for deferred taxes	(7,929)	22,821	1,374
Net amortization of investment securities available for sale	6,153	4,680	4,891
Net (gain) loss on securities	(5)	(138)	37
Accretion of discount on purchased loans, net	(27,351)	(18,978)	(10,093)
Net amortization on other borrowings	256	80	96
Amortization of subordinated deferrable interest debentures	1,940	1,655	1,345
Loan servicing asset impairment	40,067	508	0
Originations of mortgage loans held for sale	(9,067,706)	(3,791,311)	(1,768,934)
Payments received on mortgage loans held for sale	43,663	17,445	986
Proceeds from sales of mortgage loans held for sale	9,864,464	2,620,290	1,542,755
Net gains on mortgage loans held for sale	(387,124)	(74,546)	(37,336)
Originations of SBA loans	(97,017)	(41,435)	(27,820)
Proceeds from sales of SBA loans	109,296	65,862	33,675
Net gains on sales of SBA loans	(7,226)	(6,058)	(2,728)
Increase in cash surrender value of bank owned life insurance	(3,630)	(2,692)	(1,819)
Gain on bank owned life insurance proceeds	(948)	(3,583)	0
Loss on sale of loans	386	1,233	0
Changes in FDIC loss-share receivable/payable, net of cash payments received	997	3,865	5,156
Increase in interest receivable	(23,892)	(15,392)	(10,965)
Increase (decrease) in interest payable	(6,036)	5,855	2,411
Increase (decrease) in taxes payable	(12,062)	(3,597)	4,032
Change attributable to other operating activities	(97,730)	40,758	(10,761)
Net cash provided by (used in) operating activities	798,396	(940,211)	(108,803)
Investing Activities, net of effects of business combinations
Proceeds from maturities of time deposits in other banks	0	10,563	746
Purchases of securities available for sale	0	(219,352)	(290,649)
Proceeds from prepayments and maturities of securities available for sale	435,204	266,171	152,393
Proceeds from sale of securities available for sale	0	64,995	68,727
Net decrease (increase) in other investments	37,222	(44,935)	33,515
Net increase in loans	(1,733,057)	(870,132)	(68,113)
Payments received on other loans held for sale	12,954	0	0
Purchase of acquired formerly serviced portfolio	0	(103,530)	0
Purchases of premises and equipment	(18,116)	(11,581)	(10,009)
Proceeds from sale of premises and equipment	718	5,587	588
Proceeds from sales of other real estate owned	14,059	10,140	11,784
Payments paid to FDIC under loss-sharing agreements	(20,639)	(3,710)	(3,791)
Proceeds from bank owned life insurance	3,381	7,429	0
Proceeds from sales of loans	69,965	157,087	0
Net cash proceeds received from (paid in) acquisitions	(2,417)	244,181	51,495
Net cash used in investing activities	(1,200,726)	(487,087)	(53,314)
Financing Activities, net of effects of business combinations
Net increase in deposits	2,932,864	334,437	853,051
Net decrease in securities sold under agreements to repurchase	(8,994)	(22,094)	(10,254)
Proceeds from other borrowings	7,202,981	5,236,572	1,530,000
Repayment of other borrowings	(8,176,491)	(4,141,349)	(1,844,258)
Repayment of subordinated deferrable interest debentures	(5,155)	0	0
Proceeds from exercise of stock options	2,262	5,139	914
Dividends paid - common stock	(41,685)	(24,675)	(16,405)
Purchase of treasury shares	(7,995)	(18,410)	(2,062)
Net cash provided by financing activities	1,897,787	1,369,620	510,986
Net increase (decrease) in cash and cash equivalents	1,495,457	(57,678)	348,869
Cash and cash equivalents at beginning of period	621,849	679,527	330,658
Cash and cash equivalents at end of period	2,117,306	621,849	679,527
Cash paid during the year for:
Interest	94,786	125,373	67,523
Income taxes	98,609	35,865	20,026
Loans transferred to other real estate owned	7,398	6,229	10,517
Loans transferred from loans held for sale to loans held for investment	196,804	0	10,817
Loans transferred from loans held for investment to loans held for sale	179,407	8,293	8,831
Loans provided for the sales of other real estate owned	767	144	931
Initial recognition of operating lease right-of-use assets	0	27,286	0
Initial recognition of operating lease liabilities	0	29,651	0
Right-of-use assets obtained in exchange for new operating lease liabilities	54,107	6,016	0
Assets acquired in business combinations	0	5,194,955	3,064,615
Liabilities assumed in business combinations	0	4,325,642	2,415,212
Issuance of common stock in acquisitions	0	869,294	547,127
Change in unrealized gain (loss) on securities available for sale, net of tax	15,363	23,320	(3,266)
Change in unrealized gain on cash flow hedge, net of tax	$ 147	$ (499)	$ 112