Acquisitions and Divestiture - Summary of Exited Space Liability (Details) - USD ($) $ in Thousands	12 Months Ended	21 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Liability Related to Exited Space [Roll Forward]
Liability balance at beginning of the year	$ 12,961	$ 0
Charges and adjustments	69,790	13,087
Payments	(26,087)	(126)
Liability balance at end of the year	56,664	12,961	$ 56,664
CEB
Liability Related to Exited Space [Roll Forward]
Charges and adjustments			82,900
Payments			$ (26,200)
Sublease income	2,515
Disposed of by Sale \| CEB
Liability Related to Exited Space [Roll Forward]
Charges and adjustments	$ (7,500)	$ (10,100)

Business Combination, Separately Recognized Transactions, Charges And Adjustments, Net

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- Definition

Business Combination Separately Recognized Transactions, Liabilities Recognized [Roll Forward]

+ References

No definition available.

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- Definition

Business Combination, Separately Recognized Transactions, Sublease Income

+ References

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- Definition

The expenses and losses recorded for each transaction with the acquiree that was recognized separately from the acquisition of assets and assumptions of liabilities in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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- Definition

The amount of liabilities recognized recorded in a transaction with the acquiree for each transaction that is recognized separately from the acquisition of assets and assumptions of liabilities in the business combination.

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