Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Impaired loans measured at fair value on a nonrecurring basis
Impaired loans	$ 4,228	$ 9,251
OREO	1,636	7,392
Total	5,864	16,643
Level 1
Impaired loans measured at fair value on a nonrecurring basis
Impaired loans	0	0
OREO	0	0
Total	0	0
Level 2
Impaired loans measured at fair value on a nonrecurring basis
Impaired loans	0	0
OREO	0	0
Total	0	0
Level 3
Impaired loans measured at fair value on a nonrecurring basis
Impaired loans	4,228	9,251
OREO	1,636	7,392
Total	$ 5,864	$ 16,643