Revenue from Contracts with Customers - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer deposits	$ 10,208,000	$ 10,208,000		$ 8,945,000
Contract liabilities	(12,500,000)	(12,500,000)		$ (12,500,000)
Performance obligation satisfied in previous period		22,500,000
Cash payments received form customers		23,500,000
Contract assets	0	0
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized during period of adoption	(200,000)
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract liabilities	$ 1,200,000	1,200,000
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]
Revenue recognized during period of adoption		$ (579,000)
Retained Earnings | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative impact of new standard			$ 800,000