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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues:
Total revenues	$ 213,033	$ 192,713	$ 414,737	$ 385,183
Cost of revenues:
Total cost of revenues	109,492	97,660	210,588	195,368
Other expenses	82,817		163,221
Income before income taxes	20,724	20,303	40,928	42,653
Income tax provision	(5,607)	(8,722)	(11,797)	(10,835)
Net income	$ 15,117	$ 11,581	$ 29,131	$ 31,818
Net income per diluted share	$ 0.46	$ 0.35	$ 0.88	$ 0.97
Cloud and Related Services
Revenues:
Total revenues	$ 187,401	$ 157,879	$ 364,917	$ 316,656
Cost of revenues:
Total cost of revenues	95,212	77,286	182,120	153,338
Software and Services
Revenues:
Total revenues	13,331	15,896	25,290	30,954
Cost of revenues:
Total cost of revenues	8,614	10,405	17,147	21,679
Maintenance
Revenues:
Total revenues	12,301	18,938	24,530	37,573
Cost of revenues:
Total cost of revenues	5,666	$ 9,969	11,321	$ 20,351
Adjustments | ASC 606
Revenues:
Total revenues	646		346
Cost of revenues:
Total cost of revenues			(944)
Income before income taxes	646		1,290
Income tax provision	(187)		(374)
Net income	$ 459		$ 916
Net income per diluted share	$ 0.01		$ 0.03
Adjustments | Cloud and Related Services | ASC 606
Revenues:
Total revenues	$ (6,138)		$ (13,132)
Cost of revenues:
Total cost of revenues	(4,703)		(10,998)
Adjustments | Software and Services | ASC 606
Revenues:
Total revenues	1,587		3,153
Cost of revenues:
Total cost of revenues	215		452
Adjustments | Maintenance | ASC 606
Revenues:
Total revenues	5,197		10,325
Cost of revenues:
Total cost of revenues	4,488		9,602
Balances without Adoption of ASC 606 | ASC 606
Revenues:
Total revenues	213,679		415,083
Cost of revenues:
Total cost of revenues	109,492		209,644
Other expenses	82,817		163,221
Income before income taxes	21,370		42,218
Income tax provision	(5,794)		(12,171)
Net income	$ 15,576		$ 30,047
Net income per diluted share	$ 0.47		$ 0.91
Balances without Adoption of ASC 606 | Cloud and Related Services | ASC 606
Revenues:
Total revenues	$ 181,263		$ 351,785
Cost of revenues:
Total cost of revenues	90,509		171,122
Balances without Adoption of ASC 606 | Software and Services | ASC 606
Revenues:
Total revenues	14,918		28,443
Cost of revenues:
Total cost of revenues	8,829		17,599
Balances without Adoption of ASC 606 | Maintenance | ASC 606
Revenues:
Total revenues	17,498		34,855
Cost of revenues:
Total cost of revenues	$ 10,154		$ 20,923