Deferred Revenue and Performance Obligations - Summary of Deferred Revenue Balances (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Deferred Revenue Arrangement [Line Items]
Deferred revenue balance at December 31, 2017	$ 119,301
Revenue recognized during the period	(110,501)
Additions to deferred revenue during the period, including deferred revenue acquired	115,568
Deferred revenue balance at June 30, 2018	124,368
Subscription
Deferred Revenue Arrangement [Line Items]
Deferred revenue balance at December 31, 2017	110,934
Revenue recognized during the period	(94,677)
Additions to deferred revenue during the period, including deferred revenue acquired	98,095
Deferred revenue balance at June 30, 2018	114,352
Services
Deferred Revenue Arrangement [Line Items]
Deferred revenue balance at December 31, 2017	8,367
Revenue recognized during the period	(15,824)
Additions to deferred revenue during the period, including deferred revenue acquired	17,473
Deferred revenue balance at June 30, 2018	$ 10,016