Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) Customer	Sep. 30, 2018 Customer	Sep. 30, 2019 USD ($) Customer	Sep. 30, 2018 Customer	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Deferred costs current	$ 7,700,000		$ 7,700,000			$ 6,500,000
Deferred costs non current	12,000,000.0		12,000,000.0			10,300,000
Short-term investments	0		$ 0			$ 45,500,000
Subscription contracts			The Company’s subscription contracts are generally two years or longer in length, billed annually in advance, and non-cancelable.
ROU assets	13,824,000		$ 13,824,000
Lease, liability	16,228,000		$ 16,228,000
ASU 2016-02 [Member]
ROU assets					$ 14,700,000
Lease, liability					16,900,000
Deferred rent liability reversed to right-of-use asset upon adoption					$ 2,200,000
Incremental and Recoverable Costs
Deferred cost amortization period			4 years
Money Market Funds
Cash and cash equivalents fair value disclosure	$ 174,800,000		$ 174,800,000
Customer Concentration Risk | Revenue
Number of customers above 10% threshold | Customer	0	0	0	0
Customer Concentration Risk | Accounts Receivable
Number of customers above 10% threshold | Customer	0	0	0	0
Maximum
Cash and cash equivalent, FDIC insured amount	$ 250,000		$ 250,000