Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 1,456,755	$ 1,330,349	$ 2,844,533	$ 2,742,090
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,367,720	1,253,253	2,674,437	2,572,212
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	89,035	77,096	170,096	169,878
Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	1,267,027	1,168,213	2,489,019	2,414,628
Domestic Segment | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,189,314	1,101,797	2,342,163	2,267,312
Domestic Segment | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	77,713	66,416	146,856	147,316
International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	189,728	162,136	355,514	327,462
International Segment [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	178,406	151,456	332,274	304,900
International Segment [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenues	11,322	10,680	23,240	22,562
Revenue, Licensed Software, Net [Member]
Disaggregation of Revenue [Line Items]
Revenues	175,116	152,162	336,777	310,194
Revenue, Licensed Software, Net [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	157,908	138,950	306,741	285,447
Revenue, Licensed Software, Net [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	17,208	13,212	30,036	24,747
Revenue, Technology Resale, Net [Member]
Disaggregation of Revenue [Line Items]
Revenues	56,860	42,117	102,532	93,604
Revenue, Technology Resale, Net [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	51,680	36,376	89,571	80,825
Revenue, Technology Resale, Net [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,180	5,741	12,961	12,779
Revenue, Subscriptions, Net [Member]
Disaggregation of Revenue [Line Items]
Revenues	98,437	92,052	198,249	186,437
Revenue, Subscriptions, Net [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	94,222	85,281	189,605	172,217
Revenue, Subscriptions, Net [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,215	6,771	8,644	14,220
Revenue, Professional Services, Net [Member]
Disaggregation of Revenue [Line Items]
Revenues	537,078	461,082	1,031,500	972,428
Revenue, Professional Services, Net [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	457,901	409,848	892,063	862,632
Revenue, Professional Services, Net [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	79,177	51,234	139,437	109,796
Revenue, Managed Services, Net [Member]
Disaggregation of Revenue [Line Items]
Revenues	320,777	307,158	638,153	616,512
Revenue, Managed Services, Net [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	284,758	275,679	566,834	555,415
Revenue, Managed Services, Net [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	36,019	31,479	71,319	61,097
Revenue, Support and Maintenance Services, Net [Member]
Disaggregation of Revenue [Line Items]
Revenues	259,675	274,036	522,999	547,717
Revenue, Support and Maintenance Services, Net [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	211,986	220,301	429,485	443,717
Revenue, Support and Maintenance Services, Net [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	47,689	53,735	93,514	104,000
Revenue, Reimbursement Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	8,812	1,742	14,323	15,198
Revenue, Reimbursement Revenue [Member] | Domestic Segment
Disaggregation of Revenue [Line Items]
Revenues	8,572	1,778	14,720	14,375
Revenue, Reimbursement Revenue [Member] | International Segment [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 240	$ (36)	$ (397)	$ 823