Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, performance obligation, description of timing	Performance obligations are typically satisfied within three months of receipt of a customer order; therefore, a change in cost estimates will not have a material impact on the percentage of completion noted at the prior quarter end. Our typical payment terms with customers range from 30 days to 105 days
Retained earnings	$ 751,951		$ 684,540
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 751,951	$ 688,752