Deferred Revenue and Performance Obligations - Summary of Deferred Revenue Balances (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Deferred Revenue Arrangement [Line Items]
Deferred revenue balance at December 31, 2017	$ 119,301
Revenue recognized during the period	(166,114)
Additions to deferred revenue during the period, including deferred revenue acquired	170,974
Deferred revenue balance at September 30, 2018	124,161
Subscription
Deferred Revenue Arrangement [Line Items]
Deferred revenue balance at December 31, 2017	110,934
Revenue recognized during the period	(144,287)
Additions to deferred revenue during the period, including deferred revenue acquired	148,463
Deferred revenue balance at September 30, 2018	115,110
Services
Deferred Revenue Arrangement [Line Items]
Deferred revenue balance at December 31, 2017	8,367
Revenue recognized during the period	(21,827)
Additions to deferred revenue during the period, including deferred revenue acquired	22,511
Deferred revenue balance at September 30, 2018	$ 9,051