Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details) - Fair Value, measurements, nonrecurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Impaired loans measured at fair value on a nonrecurring basis
Impaired loans	$ 6,744	$ 27,348
OREO	960	2,820
Mortgage servicing rights	46,365	53,208
Total financial assets	54,069	83,376
Level 1
Impaired loans measured at fair value on a nonrecurring basis
Impaired loans	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
Impaired loans	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
Impaired loans	6,744	27,348
OREO	960	2,820
Mortgage servicing rights	46,365	53,208
Total financial assets	$ 54,069	$ 83,376