Consolidated statements of cash flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 22,873	$ 18,688	$ 23,618	$ 38,276
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense			3,231	2,450
Amortization of core deposit and other intangibles	1,205	1,254	2,408	1,983
Capitalization of mortgage servicing rights			(20,063)	(19,932)
Net change in fair value of mortgage servicing rights	14,340	8,863	35,076	13,221
Stock-based compensation expense			4,233	3,785
Provision for credit losses	24,039	881	52,003	2,272
Provision for credit losses on unfunded commitments	1,882	0	3,483	0
Provision for mortgage loan repurchases	855	89	1,227	148
Accretion of yield on purchased loans			(2,554)	(3,928)
Accretion of discounts and amortization of premiums on securities, net			2,077	1,296
Gain from securities, net	28	(52)	(35)	(95)
Originations of loans held for sale			(2,807,047)	(2,240,059)
Repurchases of loans held for sale			0	(9,670)
Proceeds from sale of loans held for sale			2,739,933	2,269,654
Gain on sale and change in fair value of loans held for sale			(113,888)	(42,425)
Net gain on other real estate owned	(86)	(277)	(137)	(238)
Loss (gain) on other assets	54	183	382	(8)
Relief of goodwill due to sale of TPO mortgage delivery channel			0	100
Provision for deferred income taxes	(8,292)	(232)	(16,380)	(4,451)
Changes in:
Operating leases			370	0
Other assets and interest receivable			(104,474)	(39,331)
Accrued expenses and other liabilities			48,799	13,803
Net cash used in operating activities			(147,738)	(13,149)
Activity in available-for-sale securities:
Sales	0	0	0	1,758
Maturities, prepayments and calls	44,703	29,353	72,360	50,167
Purchases			(59,984)	(54,218)
Net change in loans			(196,303)	(239,425)
Purchases of FHLB stock			(1,176)	(2,544)
Proceeds from sale of mortgage servicing rights			0	29,160
Purchases of premises and equipment			(4,827)	(1,011)
Proceeds from the sale of premises and equipment			0	290
Proceeds from the sale of other real estate owned	2,708	1,148	4,150	1,864
Net cash paid in business combination			(4,227)	171,032
Net cash used in investing activities			(190,007)	(42,927)
Cash flows from financing activities:
Net increase in demand deposits			891,237	71,898
Net (decrease) increase in time deposits			(82,909)	10,334
Net increase in securities sold under agreements to repurchase and federal funds purchased			5,795	16,716
Net increase in FHLB advances			0	3,235
Proceeds from other borrowings			15,000	0
Share-based compensation withholding payments			(1,162)	(2,510)
Net proceeds from sale of common stock			446	364
Dividends paid			(5,751)	(4,981)
Net cash provided by financing activities			822,656	95,056
Net change in cash and cash equivalents			484,911	38,980
Cash and cash equivalents at beginning of the period			232,681	125,356	$ 125,356
Cash and cash equivalents at end of the period	717,592	164,336	717,592	164,336	232,681
Supplemental cash flow information:
Interest paid			23,081	23,869
Taxes paid			1,590	12,823
Supplemental noncash disclosures:
Transfers from loans to other real estate owned	641	924	1,006	2,030
Transfers from other real estate owned to premises and equipment			841	0
Transfers from premises and equipment to other real estate owned			0	2,640
Loans provided for sales of other real estate owned	0	0	0	166
Transfers from loans to loans held for sale			6,317	116
Transfers from loans held for sale to loans			14,358	6,732
Stock consideration paid in business combination			35,041	0
Trade date payable - securities			5,431	1,089	$ 0
Trade date receivable - securities			0	86
Dividends declared not paid on restricted stock units	$ 77	$ 119	77	119
Decrease to retained earnings for adoption of new accounting standards			25,018	1,309
Right-of-use assets obtained in exchange for operating lease liabilities			$ 806	$ 38,249