Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 732,217		$ 684,540
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 732,217	$ 688,752
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Remaining performance obligation, expected timing of satisfaction, period	30 days
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Remaining performance obligation, expected timing of satisfaction, period	105 days