Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details) - Fair Value, measurements, nonrecurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Impaired loans measured at fair value on a nonrecurring basis
Individually evaluated loans, net of allowance for credit losses	$ 9,410	$ 24,145
OREO	170	2,736
Mortgage servicing rights	86,387	62,994
Total financial assets	95,967	89,875
Level 1
Impaired loans measured at fair value on a nonrecurring basis
Individually evaluated loans, net of allowance for credit losses	0	0
OREO	0	0
Mortgage servicing rights	0	0
Total financial assets	0	0
Level 2
Impaired loans measured at fair value on a nonrecurring basis
Individually evaluated loans, net of allowance for credit losses	0	0
OREO	0	0
Mortgage servicing rights	0	0
Total financial assets	0	0
Level 3
Impaired loans measured at fair value on a nonrecurring basis
Individually evaluated loans, net of allowance for credit losses	9,410	24,145
OREO	170	2,736
Mortgage servicing rights	86,387	62,994
Total financial assets	$ 95,967	$ 89,875