Revenue Recognition - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 60,594,000	$ 50,024,000	$ 48,837,000
Impairment charges related to contract assets	$ 0
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Payment terms	30 days
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Payment terms	90 days
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect of change on equity or net assets	$ 4,100,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ (5,031,000)