Restructuring Charges - Reconciliation of Beginning and Ending Liability Balances by Major Restructuring Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			$ 2,276
Restructuring charges	$ 975	$ 1,069	1,967	$ 1,285
Cash payments			(1,832)
Adjustment to liability			214
Balance at June 30, 2016	2,625		2,625
Marketing Events Group Consolidation | Employee Severance
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			751
Restructuring charges			1,455
Cash payments			(1,126)
Balance at June 30, 2016	1,080		1,080
Marketing Events Group Consolidation | Facility Closing
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			1,291
Restructuring charges			9
Cash payments			(213)
Balance at June 30, 2016	1,087		1,087
Other Restructuring | Employee Severance
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2015			234
Restructuring charges			503
Cash payments			(493)
Adjustment to liability			214
Balance at June 30, 2016	$ 458		$ 458