Segments and Geographic Areas - Reconciliation of Segment Assets to Total Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Oct. 02, 2016	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and cash equivalents
Total cash and cash equivalents	$ 134,929			$ 113,329	$ 114,934	$ 119,554
Accounts receivable, net
Total accounts receivable, net	284,042			285,048
Goodwill
Total goodwill	565,036		$ 237,234	458,409
Intangible assets, net
Total intangible assets, net	184,184			230,680
Property and equipment, net
Total property and equipment, net	95,217			102,337
Total assets
Total assets	1,412,592			1,338,552
CEB Segment [Member]
Cash and cash equivalents
Total cash and cash equivalents	67,154			92,493
Accounts receivable, net
Total accounts receivable, net	223,812			220,678
Goodwill
Total goodwill	293,136			129,386
Intangible assets, net
Total intangible assets, net	74,937			47,051
Property and equipment, net
Total property and equipment, net	81,753			86,661
Total assets
Total assets	888,892			722,806
CEB Talent Assessment Segment [Member]
Cash and cash equivalents
Total cash and cash equivalents	67,775			20,836
Accounts receivable, net
Total accounts receivable, net	60,230			64,370
Goodwill
Total goodwill	271,900	$ 286,400		329,023
Intangible assets, net
Total intangible assets, net	109,247			183,629
Property and equipment, net
Total property and equipment, net	13,464			15,676
Total assets
Total assets	$ 523,700			$ 615,746