Revenue from Contracts with Customers - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 50,551,000			$ 39,924,000
Amortization of commissions assets	200,000
Capitalized contract costs		$ 0
Revenue recognized	64,878,000	$ 53,121,000
Unbilled contracts	38,263,000
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized	$ 55,600,000
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			$ 2,700,000
Commission asset balance			3,500,000
Deferred tax liability			$ 800,000