Restructuring Charges - Reconciliation of Beginning and Ending Liability Balances by Major Restructuring Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			$ 2,276
Restructuring charges	$ 1,697	$ 257	3,664	$ 1,542
Cash payments			(2,518)
Adjustment to liability			169
Balance at September 30, 2016	3,591		3,591
Marketing Events Group Consolidation | Employee Severance
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			751
Restructuring charges			3,448
Cash payments			(1,922)
Balance at September 30, 2016	2,277		2,277
Marketing Events Group Consolidation | Facility Closing
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			1,291
Restructuring charges			(283)
Cash payments			(246)
Adjustment to liability			193
Balance at September 30, 2016	955		955
Other Restructuring | Employee Severance
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			234
Restructuring charges			499
Cash payments			(350)
Adjustment to liability			(24)
Balance at September 30, 2016	$ 359		$ 359