Revenues - Disaggregation of Revenues by Source (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Disaggregation of revenue	$ 421,929	$ 407,699
Software-enabled Services [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenue	294,803	276,452
Maintenance and Term Licenses [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenue	107,756	110,557
Perpetual Licenses [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenue	4,400	2,828
Professional Services [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenue	$ 14,970	$ 17,862