Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ (194)	$ 77
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0		$ 0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0		0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 2,108		$ 2,214