Revenue Recognition - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Unbilled receivables related to service	$ 2,100,000
Deferred sales commissions on initial contracts sold	16,800,000
Amortization expense for the deferred costs	5,500,000	$ 5,900,000
impairment loss related to costs capitalized	0
Capitalized commissions	6,503,000	$ 2,429,000
Revenue remaining performance obligation	201,700,000
Subscription Services
Disaggregation Of Revenue [Line Items]
Revenue recognized	$ 62,500,000