Disclosures about Fair Value of Assets and Liabilities - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financial assets:
Loans held for sale	$ 23,357	$ 11,886
Carrying Value
Financial assets:
Cash and cash equivalents	364,976	336,524
Securities purchased under agreements to resell	6,760	6,875
FHLB stock	18,808	7,974
Loans held for sale	2,475,181	820,569
Loans, net	2,742,088	2,045,423
Interest receivable	18,780	13,827
Financial liabilities:
Deposits	5,499,649	3,231,086
Lines of credit		33,150
Short-term subordinated debt	12,000	10,582
FHLB advances	147,673	151,721
Interest payable	13,130	4,132
Fair Value
Financial assets:
Cash and cash equivalents	364,976	336,524
Securities purchased under agreements to resell	6,760	6,875
FHLB stock	18,808	7,974
Loans held for sale	2,475,181	820,569
Loans, net	2,728,683	2,041,772
Interest receivable	18,780	13,827
Financial liabilities:
Deposits	5,500,297	3,230,397
Lines of credit		33,150
Short-term subordinated debt	12,000	10,582
FHLB advances	147,772	151,723
Interest payable	13,130	4,132
Level 1 | Fair Value
Financial assets:
Cash and cash equivalents	364,976	336,524
Financial liabilities:
Deposits	3,248,689	2,550,632
Level 2 | Fair Value
Financial assets:
Securities purchased under agreements to resell	6,760	6,875
FHLB stock	18,808	7,974
Loans held for sale	2,475,181	820,569
Interest receivable	18,780	13,827
Financial liabilities:
Deposits	2,251,608	679,765
Lines of credit		33,150
Short-term subordinated debt	12,000	10,582
FHLB advances	147,772	151,723
Interest payable	13,130	4,132
Level 3 | Fair Value
Financial assets:
Loans, net	$ 2,728,683	$ 2,041,772