Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands						9 Months Ended
	Aug. 03, 2021	Nov. 23, 2020	Oct. 26, 2020	Oct. 01, 2020	Feb. 28, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Purchase price, net of cash						$ 14,314	$ 885,323
Goodwill		$ 2,861				$ 6,198,701		$ 6,252,636	$ 1,328,045
Decision Resources Group
Business Acquisition [Line Items]
Accounts receivable					$ 52,193
Prepaid expenses					4,295
Other current assets					68,001
Property and equipment, net					4,136
Other intangible assets					491,366
Other non-current assets					2,960
Operating lease right-of-use assets					25,099
Total assets					648,050
Accounts payable					3,474
Accrued expenses and other current liabilities					88,561
Current portion of deferred revenue					35,126
Current portion of operating lease liabilities					5,188
Deferred income taxes					47,467
Non-current portion of deferred revenue					936
Operating lease liabilities					20,341
Total liabilities					201,093
Fair value of acquired identifiable assets and liabilities					446,957
Goodwill					497,263
Cash acquired					20,777
Decision Resources Group | Software Development
Business Acquisition [Line Items]
Other intangible assets					3,966
CPA Global
Business Acquisition [Line Items]
Accounts receivable				$ 380,259
Prepaid expenses				27,437
Other current assets				215,734
Property and equipment, net				13,290
Other intangible assets				4,920,317
Deferred income taxes				21,027
Other non-current assets				25,736
Operating lease right-of-use assets				30,649
Total assets				5,634,449
Accounts payable				53,791
Accrued expenses and other current liabilities				458,551
Current portion of deferred revenue				181,365
Current portion of operating lease liabilities				7,738
Deferred income taxes				288,541
Non-current portion of deferred revenue				16,771
Other non-current liabilities				43,785
Operating lease liabilities				23,615
Total liabilities				1,074,157
Fair value of acquired identifiable assets and liabilities				4,560,292
Business Combination, Consideration Transferred, Net of Cash Acquired				8,740,324
Goodwill				4,180,032
Cash acquired				$ 99,275
IncoPat
Business Acquisition [Line Items]
Accounts receivable			$ 1,107
Prepaid expenses			168
Other current assets			100
Property and equipment, net			354
Other intangible assets			21,957
Other non-current assets			283
Total assets			23,969
Accounts payable			73
Accrued expenses and other current liabilities			843
Current portion of deferred revenue			6,445
Deferred income taxes			4,802
Other non-current liabilities			283
Total liabilities			12,446
Fair value of acquired identifiable assets and liabilities			11,523
Purchase price, net of cash			52,133
Goodwill			40,610
Cash acquired			$ 844
Hanlim IPS
Business Acquisition [Line Items]
Accounts receivable		44
Prepaid expenses		7
Other current assets		844
Property and equipment, net		75
Other intangible assets		8,805
Other non-current assets		94
Total assets		9,869
Accounts payable		27
Accrued expenses and other current liabilities		1,512
Deferred income taxes		1,937
Total liabilities		3,476
Fair value of acquired identifiable assets and liabilities		6,393
Purchase price, net of cash		9,254
Cash acquired		$ 2,191
DRG
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Net of Cash Acquired					$ 944,220
BioInfogate
Business Acquisition [Line Items]
Accounts receivable	$ 366
Prepaid expenses	3
Other current assets	102
Property and equipment, net	21
Other intangible assets	6,280
Deferred income taxes	184
Other non-current assets	6
Total assets	6,962
Accounts payable	12
Accrued expenses and other current liabilities	82
Current portion of deferred revenue	1,247
Total liabilities	1,341
Fair value of acquired identifiable assets and liabilities	5,621
Purchase price, net of cash	16,918
Goodwill	11,297
Cash acquired	$ 2,069