Disclosures about Fair Value of Assets and Liabilities - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial assets:
Loans held for sale	$ 26,296	$ 40,044
Carrying Value
Financial assets:
Cash and cash equivalents	802,576	179,728
Securities purchased under agreements to resell	5,923	6,580
FHLB stock	70,767	70,656
Loans held for sale	3,426,983	3,030,110
Loans, net	5,431,227	5,507,926
Interest receivable	21,894	21,770
Financial liabilities:
Deposits	8,947,319	7,408,066
Short-term subordinated debt	17,000	14,960
FHLB advances	556,979	1,221,071
Other borrowing	235,157
Federal Reserve discount window/PPPLF advances		112,225
Interest payable	2,477	1,476
Fair Value
Financial assets:
Cash and cash equivalents	802,576	179,728
Securities purchased under agreements to resell	5,923	6,580
FHLB stock	70,767	70,656
Loans held for sale	3,426,983	3,030,110
Loans, net	5,389,595	5,484,824
Interest receivable	21,894	21,770
Financial liabilities:
Deposits	8,948,327	7,410,759
Short-term subordinated debt	17,000	14,960
FHLB advances	556,992	1,221,870
Other borrowing	235,157
Federal Reserve discount window/PPPLF advances		112,225
Interest payable	2,477	1,476
Level 1 | Fair Value
Financial assets:
Cash and cash equivalents	802,576	179,728
Financial liabilities:
Deposits	7,707,121	7,051,413
Level 2 | Fair Value
Financial assets:
Securities purchased under agreements to resell	5,923	6,580
FHLB stock	70,767	70,656
Loans held for sale	3,426,983	3,030,110
Interest receivable	21,894	21,770
Financial liabilities:
Deposits	1,241,206	359,346
Short-term subordinated debt	17,000	14,960
FHLB advances	556,992	1,221,870
Other borrowing	235,157
Federal Reserve discount window/PPPLF advances		112,225
Interest payable	2,477	1,476
Level 3 | Fair Value
Financial assets:
Loans, net	$ 5,389,595	$ 5,484,824