Recent Accounting Pronouncements - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 325,878			$ 274,836	$ 274,562
Accumulated Other Comprehensive Income (Loss), Net of Tax	6,174	$ 6,340	$ 4,579		$ 4,366	$ 4,290	$ 5,898	$ 7,016	$ 7,721
Accounting Standards Update 2018-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	350
Accumulated Other Comprehensive Income (Loss), Net of Tax	350
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 894			$ 274