Fair Value Measurement - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Allowance for Loan and Lease Loss
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Valuation allowance, period increase (decrease)	$ 138	$ 167
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount on appraisals of secured collateral (as a percent)		10.00%
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount on appraisals of secured collateral (as a percent)		50.00%