Summary of Significant Accounting Policies - Summary of Impacts of Adopting ASC 606 on Condensed Statement of Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Cloud and related services	$ 177,516	$ 158,777
Software and services	11,959	15,058
Maintenance	12,229	18,635
Total revenues	201,704	192,470
Cost of revenues:
Cloud and related services	86,908	76,052
Software and services	8,533	11,274
Maintenance	5,655	10,382
Total cost of revenues	101,096	97,708
Other expenses	80,404
Income before income taxes	20,204	22,350
Income tax provision	(6,190)	(2,113)
Net income	$ 14,014	$ 20,237
Net income per diluted share	$ 0.42	$ 0.62
Adjustments | ASU 606
Revenues:
Cloud and related services	$ (6,994)
Software and services	1,566
Maintenance	5,128
Total revenues	(300)
Cost of revenues:
Cloud and related services	(6,295)
Software and services	237
Maintenance	5,114
Total cost of revenues	(944)
Income before income taxes	644
Income tax provision	(187)
Net income	$ 457
Net income per diluted share	$ 0.02
Balances without Adoption of ASC 606 | ASU 606
Revenues:
Cloud and related services	$ 170,522
Software and services	13,525
Maintenance	17,357
Total revenues	201,404
Cost of revenues:
Cloud and related services	80,613
Software and services	8,770
Maintenance	10,769
Total cost of revenues	100,152
Other expenses	80,404
Income before income taxes	20,848
Income tax provision	(6,377)
Net income	$ 14,471
Net income per diluted share	$ 0.44