Acquisitions - Summary of the Allocation of the Purchase Price to the Fair Value of the Assets and Liabilities Assumed (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Apr. 05, 2017	Mar. 09, 2017	Dec. 31, 2016
Assets:
Cash		$ 199,558
Fees receivable		185,144
Prepaid expenses and other current assets		32,460
Property, equipment and leasehold improvements		60,463
Goodwill	$ 3,169,893	2,427,974		$ 738,453
Finite-lived intangible assets		1,589,890
Other assets		169,694
Total assets		4,665,183
Liabilities:
Accounts payable and accrued liabilities		135,925
Deferred revenues (current)		260,544
Other liabilities		615,686
Total liabilities		1,012,155
Net assets acquired		3,653,028
CEB
Assets:
Cash		194,706
Fees receivable		176,867
Prepaid expenses and other current assets		31,293
Property, equipment and leasehold improvements		59,800
Goodwill		2,318,195
Finite-lived intangible assets		1,574,000
Other assets		157,373
Total assets		4,512,234
Liabilities:
Accounts payable and accrued liabilities		132,875
Deferred revenues (current)		247,344
Other liabilities		613,186
Total liabilities		993,405
Net assets acquired		$ 3,518,829
L2, Inc.
Assets:
Cash			$ 4,852
Fees receivable			8,277
Prepaid expenses and other current assets			1,167
Property, equipment and leasehold improvements			663
Goodwill			109,779
Finite-lived intangible assets			15,890
Other assets			12,321
Total assets			152,949
Liabilities:
Accounts payable and accrued liabilities			3,050
Deferred revenues (current)			13,200
Other liabilities			2,500
Total liabilities			18,750
Net assets acquired			$ 134,199