Fair Value of Assets and Liabilities - Schedule of Difference between Aggregate Fair Value and Aggregate Unpaid Principal Balance (Details) - Residential mortgage loans held for sale - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Option Quantitative Disclosures [Line Items]
Aggregate Fair Value	$ 21,965	$ 82,565
Aggregate Unpaid Principal	21,376	78,577
Aggregate Fair Value Less Aggregate Unpaid Principal	$ 589	$ 3,988