Fair Value Measurements - Summarizes Differences Between Fair Value and Principal Balance for Mortgage Loans Held for Sale Measure at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Aggregate Fair Value
Summarizes differences between fair value and principal balance for mortgage loans held for sale measure at fair value
Mortgage loans held for sale measured at fair value	$ 399,773	$ 318,272
Aggregate Unpaid Principal Balance
Summarizes differences between fair value and principal balance for mortgage loans held for sale measure at fair value
Mortgage loans held for sale measured at fair value	378,785	308,160
Difference
Summarizes differences between fair value and principal balance for mortgage loans held for sale measure at fair value
Mortgage loans held for sale measured at fair value	$ 20,988	$ 10,112