Restructuring Charges - Reconciliation of Beginning and Ending Liability Balances by Major Restructuring Activity (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2012				$ 1,944				$ 5,698	$ 1,944	$ 5,698	$ 7,224
Restructuring charges (recoveries)	$ 1,414	$ 257	$ 1,069	216	$ (177)	$ 234	$ 1,369	211	2,956	1,637	3,793
Cash payments									(2,572)	(5,276)	(4,841)
Adjustment to liability									(52)	(115)	(478)
Balance at December 31, 2013	2,276				1,944				2,276	1,944	5,698
Marketing & Events Group | Severance & Employee Benefits
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2012				543				1,240	543	1,240	720
Restructuring charges (recoveries)									1,767	2,358	2,931
Cash payments									(1,514)	(3,055)	(2,411)
Adjustment to liability									(45)
Balance at December 31, 2013	751				543				751	543	1,240
Marketing & Events Group | Facilities
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2012				1,161				3,565	1,161	3,565	5,571
Restructuring charges (recoveries)									587	(828)	(315)
Cash payments									(457)	(1,376)	(1,691)
Adjustment to liability										(200)
Balance at December 31, 2013	1,291				1,161				1,291	1,161	3,565
Other Restructuring | Severance & Employee Benefits
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2012				$ 240				$ 893	240	893
Restructuring charges (recoveries)									602	107	1,869
Cash payments									(601)	(845)	(498)
Adjustment to liability									(7)	85	(478)
Balance at December 31, 2013	$ 234				$ 240				$ 234	$ 240	893
Other Restructuring | Facilities
Restructuring Cost And Reserve [Line Items]
Balance at December 31, 2012											933
Restructuring charges (recoveries)											(692)
Cash payments											$ (241)