Consolidated statements of cash flows - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 18,688,000	$ 22,065,000	$ 38,276,000	$ 41,819,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	1,278,000	1,132,000	2,450,000	2,238,000
Amortization of core deposit and other intangibles	1,254,000	802,000	1,983,000	1,655,000
Capitalization of mortgage servicing rights			(19,932,000)	(29,814,000)
Net change in fair value of mortgage servicing rights	8,863,000	15,000	13,221,000	(3,528,000)
Stock-based compensation expense			3,785,000	3,819,000
Provision for loan losses	881,000	1,063,000	2,272,000	1,380,000
Provision for mortgage loan repurchases	89,000	206,000	148,000	392,000
Accretion of yield on purchased loans			(3,928,000)	(3,615,000)
Accretion of discounts and amortization of premiums on securities, net			1,296,000	1,378,000
(Gain) loss from securities, net	(52,000)	42,000	(95,000)	89,000
Originations of loans held for sale			(2,240,059,000)	(3,287,255,000)
Repurchases of loans held for sale			(9,670,000)	(3,222,000)
Proceeds from sale of loans held for sale			2,269,654,000	3,441,316,000
Gain on sale and change in fair value of loans held for sale			(42,425,000)	(48,109,000)
Net (gain) loss or write-downs of other real estate owned	(277,000)	(23,000)	(238,000)	163,000
(Gain) loss on other assets	183,000	155,000	(8,000)	87,000
Impairment of goodwill			100,000	0
Provision for deferred income taxes	(232,000)	5,599,000	(4,451,000)	11,081,000
Changes in:
Other assets and interest receivable			(39,331,000)	(8,435,000)
Accrued expenses and other liabilities			13,803,000	(42,630,000)
Net cash (used in) provided by operating activities			(13,149,000)	78,809,000
Activity in available-for-sale securities:
Sales	0	0	1,758,000	221,000
Maturities, prepayments and calls	29,353,000	18,005,000	50,167,000	34,508,000
Purchases			(54,218,000)	(121,108,000)
Purchases of FHLB stock			(2,544,000)	(1,229,000)
Net increase in loans			(239,425,000)	(239,188,000)
Proceeds from sale of mortgage servicing rights			29,160,000	0
Purchases of premises and equipment			(1,011,000)	(6,597,000)
Proceeds from the sale of premises and equipment			290,000	0
Proceeds from the sale of other real estate owned			1,864,000	2,209,000
Net cash received in business combination			171,032,000		$ 0
Net cash used in investing activities			(42,927,000)	(331,184,000)
Cash flows from financing activities:
Net increase in demand deposits			71,898,000	203,688,000
Net increase in time deposits			10,334,000	41,780,000
Net increase in securities sold under agreements to repurchase and federal funds purchased			16,716,000	4,225,000
Net increase (decrease) in FHLB advances			3,235,000	(8,927,000)
Share based compensation witholding obligation			(2,510,000)	(2,555,000)
Net proceeds from sale of common stock			364,000	669,000
Dividends paid			(4,981,000)	(1,839,000)
Net cash provided by financing activities			95,056,000	237,041,000
Net change in cash and cash equivalents			38,980,000	(15,334,000)
Cash and cash equivalents at beginning of the period			125,356,000	119,751,000	119,751,000
Cash and cash equivalents at end of the period	164,336,000	104,417,000	164,336,000	104,417,000	125,356,000
Supplemental cash flow information:
Interest paid			23,869,000	13,269,000
Taxes paid			12,823,000	19,112,000
Supplemental noncash disclosures:
Transfers from loans to other real estate owned	924,000	384,000	2,030,000	1,014,000
Transfers from premises and equipment to other real estate owned	2,640,000	0	2,640,000	0
Loans provided for sales of other real estate owned	0	325,000	166,000	445,000
Transfers from loans to loans held for sale			116,000	5,504,000
Transfers from loans held for sale to loans			6,732,000		$ 0
Trade date payable - securities			1,089,000	0
Trade date receivable - securities			86,000	0
Dividends declared not paid on restricted stock units	$ 119,000	$ 70,000	119,000	70,000
Decrease to retained earnings for adoption of new accounting standards			1,309,000	109,000
Right-of-use assets obtained in exchange for operating lease liabilities			38,249,000	0
GNMA
Supplemental noncash disclosures:
Derecognition of rebooked GNMA delinquent loans			$ 0	$ 43,035,000