Consolidated statements of cash flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 83,814	$ 80,236	$ 52,398
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	5,176	4,334	4,316
Amortization of core deposit and other intangibles	4,339	3,185	1,995
Capitalization of mortgage servicing rights	(42,151)	(54,913)	(58,984)
Net change in fair value of mortgage servicing rights	26,299	2,763	4,023
Stock-based compensation expense	7,089	7,207	6,760
Provision for loan losses	7,053	5,398	(950)
Provision for mortgage loan repurchases	362	174	810
Accretion of yield on purchased loans	(8,556)	(7,608)	(5,419)
Accretion of discounts and amortization of premiums on securities, net	3,026	2,768	2,693
(Gain) loss from securities, net	(57)	116	(285)
Originations of loans held for sale	(4,540,652)	(5,958,066)	(6,331,458)
Repurchases of loans held for sale	(9,919)	(12,232)	0
Proceeds from sale of loans held for sale	4,662,728	6,260,532	6,408,198
Gain on sale and change in fair value of loans held for sale	(100,228)	(88,743)	(107,189)
Loss on sale of mortgage servicing rights	0	0	249
Net (gain) loss or write-downs of other real estate owned	(545)	99	(774)
Loss (gain) on other assets	104	(328)	664
Relief of goodwill	100	0	0
Provision for deferred income taxes	(1,916)	6,359	6,458
Changes in:
Other assets and interest receivable	(45,180)	(22,966)	6,478
Accrued expenses and other liabilities	13,019	(16,107)	47,627
Net cash provided by operating activities	63,905	212,208	37,610
Activity in available-for-sale securities:
Sales	24,498	2,742	94,743
Maturities, prepayments and calls	113,018	73,066	83,344
Purchases	(151,425)	(203,844)	(81,353)
Net increase in loans	(364,975)	(491,774)	(241,379)
Purchases of FHLB stock	(2,544)	(2,020)	0
Proceeds from sale of mortgage servicing rights	29,160	39,428	11,686
Purchases of premises and equipment	(6,812)	(10,144)	(4,545)
Proceeds from the sale of premises and equipment	1,275	357	39
Proceeds from the sale of other real estate owned	3,860	4,819	5,438
Proceeds from the sale of other assets	0	869	0
Net cash received (paid) in business combination (See Note 2)	171,032	0	(135,141)
Net cash used in investing activities	(182,913)	(586,501)	(267,168)
Cash flows from financing activities:
Net increase in demand deposits	249,348	75,906	14,682
Net (decrease) increase in time deposits	(75,004)	431,416	(1,367)
Net increase in securities sold under agreements to repurchase and federal funds purchased	(908)	788	(7,268)
Net increase (decrease) in FHLB advances	68,235	(120,607)	53,579
Share based compensation witholding payment	(6,097)	(2,664)	0
Net proceeds from sale of common stock	804	1,196	153,356
Dividends paid	(10,045)	(6,137)	0
Net cash provided by financing activities	226,333	379,898	212,982
Net change in cash and cash equivalents	107,325	5,605	(16,576)
Cash and cash equivalents at beginning of the period	125,356	119,751	136,327
Cash and cash equivalents at end of the period	232,681	125,356	119,751
Supplemental cash flow information:
Interest paid	55,051	31,992	15,470
Taxes paid	25,920	24,387	22,292
Supplemental noncash disclosures:
Transfers from loans to other real estate owned	5,487	2,138	3,605
Transfers from premises and equipment to other real estate owned at fair value	4,290	0	3,466
Loans provided for sales of other real estate owned	166	1,019	256
Transfers from loans to loans held for sale	7,891	11,888	0
Transfers from loans held for sale to loans	12,259	14,732	11,706
Stock consideration paid in business combination	0	0	52,284
Trade date payable - securities	0	2,120	348
Dividends declared not paid on restricted stock units	149	226	0
Decrease to retained earnings for adoption of new accounting standards (See Note 1)	1,309	109	0
Right-of-use assets obtained in exchange for operating lease liabilities	37,916	0	0
Fair value election of mortgage servicing rights	0	0	1,011
GNMA
Supplemental noncash disclosures:
Transfers from loans held for sale to loans	0	0	43,035
Derecognition of rebooked GNMA delinquent loans	$ 0	$ 43,035	$ 0