Summary of Significant Accounting Policies - AOCL (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ (766)
Balance	(904)
Unrealized (loss) gain on available-for-sale securities, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(766)
Increase	(170)
Reclassification adjustment	32
Balance	(904)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(766)
Increase	(170)
Reclassification adjustment	32
Balance	$ (904)