Acquisitions and Divestitures - Summary of Exited Space Liability (Details) - CEB	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Liability Related to Exited Space [Roll Forward]
Beginning liability balance	$ 12,961
Charges and adjustments, net	44,230,000	$ 57,300,000
Payments	(4,734,000)	(4,900,000)
Ending liability balance	52,457,000	52,457,000
Total anticipated exit costs	$ 61,200,000	$ 61,200,000