Fair Value Measurements - Financial Instruments Carried at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Loans, held for sale, at fair value	$ 473,078	$ 340,288
Paycheck Protection Program loans	38,388	74,931
Derivative instruments, at fair value	12,529	16,363
Residential mortgage servicing rights, at fair value	98,542	76,840
Liabilities:
Derivative instruments, at fair value	4,403	11,604
Recurring
Assets:
Loans, held for sale, at fair value	473,078	340,288
Loans, net at fair value	13,618	13,795
Paycheck Protection Program loans	38,388	74,931
Mortgage backed securities, at fair value	682,948	88,011
Derivative instruments, at fair value	12,529	16,363
Residential mortgage servicing rights, at fair value	98,542	76,840
Total assets	1,319,103	610,228
Liabilities:
Derivative instruments, at fair value	4,403	11,604
Total liabilities	4,403	11,604
Recurring | Level 2 inputs
Assets:
Loans, held for sale, at fair value	473,078	340,288
Mortgage backed securities, at fair value	677,315	62,880
Derivative instruments, at fair value	805
Total assets	1,151,198	403,168
Liabilities:
Derivative instruments, at fair value	4,403	11,604
Total liabilities	4,403	11,604
Recurring | Level 3 inputs
Assets:
Loans, net at fair value	13,618	13,795
Paycheck Protection Program loans	38,388	74,931
Mortgage backed securities, at fair value	5,633	25,131
Derivative instruments, at fair value	11,724	16,363
Residential mortgage servicing rights, at fair value	98,542	76,840
Total assets	$ 167,905	$ 207,060