Goodwill - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Oct. 02, 2016	Dec. 31, 2016	Jun. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2016
Goodwill [Line Items]
Impairment loss				$ 69,441		$ 39,700
Goodwill impairment loss				67,890
Intangible asset impairment loss				22,350	$ 20,800
Intangible assets carrying value		$ 1,500		1,500
Goodwill		565,036		565,036	458,409		$ 237,234
Customer Relationships [Member]
Goodwill [Line Items]
Intangible asset impairment loss			$ 20,800	$ 20,800	20,800
Evanta [Member]
Goodwill [Line Items]
Impairment loss		69,400
Goodwill impairment loss		67,900
Intangible asset impairment loss		1,500
Discount rate				12.50%
Long term growth rate				4.00%
Evanta [Member] | Intangible Assets [Member]
Goodwill [Line Items]
Deferred income tax liability		10,900		$ 10,900
Reduction in deferred tax liability				600
CEB Talent Assessment Segment [Member]
Goodwill [Line Items]
Carrying value of reporting unit	$ 439,700
Goodwill	286,400	$ 271,900		$ 271,900	$ 329,023
Amortizable intangible assets	$ 126,300
Percentage exceeded in estimated value over carrying value	9.00%
PDRI [Member]
Goodwill [Line Items]
Impairment loss			39,700
Goodwill impairment loss			18,900
PDRI [Member] | Customer Relationships [Member]
Goodwill [Line Items]
Intangible asset impairment loss			$ 20,800