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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Total revenues	$ 213,055	$ 199,195	$ 627,792	$ 584,378
Cost of revenues:
Total cost of revenues	109,052	99,717	319,640	295,085
Other expenses	83,511		246,732
Income before income taxes	20,492	23,386	61,420	66,039
Income tax provision	(4,391)	(8,806)	(16,188)	(19,641)
Net income	$ 16,101	$ 14,580	$ 45,232	$ 46,398
Net income per diluted share	$ 0.49	$ 0.44	$ 1.37	$ 1.41
Cloud and Related Services
Revenues:
Total revenues	$ 186,473	$ 164,789	$ 551,390	$ 481,445
Cost of revenues:
Total cost of revenues	95,092	79,856	277,212	233,194
Software and Services
Revenues:
Total revenues	14,283	15,726	39,573	46,680
Cost of revenues:
Total cost of revenues	8,669	9,725	25,816	31,404
Maintenance
Revenues:
Total revenues	12,299	18,680	36,829	56,253
Cost of revenues:
Total cost of revenues	5,291	$ 10,136	16,612	$ 30,487
Adjustments | ASC 606
Revenues:
Total revenues	644		990
Cost of revenues:
Total cost of revenues			(944)
Income before income taxes	644		1,934
Income tax provision	(187)		(561)
Net income	$ 457		$ 1,373
Net income per diluted share	$ 0.01		$ 0.04
Adjustments | Cloud and Related Services | ASC 606
Revenues:
Total revenues	$ (6,162)		$ (19,294)
Cost of revenues:
Total cost of revenues	(4,544)		(15,542)
Adjustments | Software and Services | ASC 606
Revenues:
Total revenues	1,589		4,742
Cost of revenues:
Total cost of revenues	208		660
Adjustments | Maintenance | ASC 606
Revenues:
Total revenues	5,217		15,542
Cost of revenues:
Total cost of revenues	4,336		13,938
Balances without Adoption of ASC 606 | ASC 606
Revenues:
Total revenues	213,699		628,782
Cost of revenues:
Total cost of revenues	109,052		318,696
Other expenses	83,511		246,732
Income before income taxes	21,136		63,354
Income tax provision	(4,578)		(16,749)
Net income	$ 16,558		$ 46,605
Net income per diluted share	$ 0.50		$ 1.41
Balances without Adoption of ASC 606 | Cloud and Related Services | ASC 606
Revenues:
Total revenues	$ 180,311		$ 532,096
Cost of revenues:
Total cost of revenues	90,548		261,670
Balances without Adoption of ASC 606 | Software and Services | ASC 606
Revenues:
Total revenues	15,872		44,315
Cost of revenues:
Total cost of revenues	8,877		26,476
Balances without Adoption of ASC 606 | Maintenance | ASC 606
Revenues:
Total revenues	17,516		52,371
Cost of revenues:
Total cost of revenues	$ 9,627		$ 30,550