Acquisitions, Intangible Assets and Goodwill - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Sep. 03, 2019	Apr. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Acquisitions Intangible Assets And Goodwill [Line Items]
Cash consideration					$ 114,603	$ 0
Amortization expense related to capitalized internal-use software			$ 4,100	$ 5,000	11,500	16,300
Amortization expense			2,521	$ 1,053	5,715	$ 3,237
Capitalized internal-use software, net			34,188		34,188		$ 33,280
Capitalized Internal-Use Software Net in Development Phase
Acquisitions Intangible Assets And Goodwill [Line Items]
Capitalized internal-use software, net			10,500		10,500
General and Administrative Expenses
Acquisitions Intangible Assets And Goodwill [Line Items]
Acquisition-related incremental expenses			$ 700		$ 1,700
GetFeedback, Inc
Acquisitions Intangible Assets And Goodwill [Line Items]
Closing date of acquisition	Sep. 03, 2019
Percentage of outstanding shares purchased	100.00%
Business combination, consideration paid in common stock	376,333
Business combination, fair value of common stock	$ 16.24
Cash consideration	$ 61,500
Net cash acquired	700
Business combination, total purchase consideration	$ 68,300
Usabilla Holding B.V.
Acquisitions Intangible Assets And Goodwill [Line Items]
Closing date of acquisition		Apr. 01, 2019
Percentage of outstanding shares purchased		100.00%
Business combination, consideration paid in common stock		1,644,413
Business combination, fair value of common stock		$ 18.30
Cash consideration		$ 53,100
Net cash acquired		1,100
Business combination, total purchase consideration		$ 84,300
Usabilla Holding B.V. | Certain Employees of Acquired Company
Acquisitions Intangible Assets And Goodwill [Line Items]
Business acquisition, additional consideration granted		299,798
Stock-based compensation, requisite service period		3 years