Restructuring Charges - Reconciliation of Beginning and Ending Liability Balances by Major Restructuring Activity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				$ 5,698				$ 7,224	$ 5,698	$ 7,224	$ 6,950
Restructuring charges	(177)	234	1,369	211	1,661	639	773	720	1,637	3,793	4,942
Restructuring liabilities									(5,276)	(4,841)	(4,694)
Adjustment to liability									(115)	(478)	24
Foreign currency translation adjustment											2
Closing Balance	1,944				5,698				1,944	5,698	7,224
Marketing & Events Group
Reconciliation of beginning and ending liability balances by major restructuring activity
Restructuring charges									(278)	(409)	3,479
Marketing & Events Group | Severance & Employee Benefits
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				1,240				720	1,240	720	831
Restructuring charges									2,358	2,931	2,506
Restructuring liabilities									(3,055)	(2,411)	(2,670)
Adjustment to liability									0	0	51
Foreign currency translation adjustment											2
Closing Balance	543				1,240				543	1,240	720
Marketing & Events Group | Facilities
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				3,565				5,571	3,565	5,571	4,819
Restructuring charges									(828)	(315)	2,346
Restructuring liabilities									(1,376)	(1,691)	(1,567)
Adjustment to liability									(200)	0	(27)
Foreign currency translation adjustment											0
Closing Balance	1,161				3,565				1,161	3,565	5,571
Other Restructuring | Severance & Employee Benefits
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				893				0	893	0	24
Restructuring charges									107	1,869	90
Restructuring liabilities									(845)	(498)	(114)
Adjustment to liability									85	(478)	0
Foreign currency translation adjustment											0
Closing Balance	240				893				240	893	0
Other Restructuring | Facilities
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				0				933	0	933	1,276
Restructuring charges									0	(692)	0
Restructuring liabilities									0	(241)	(343)
Adjustment to liability									0	0	0
Foreign currency translation adjustment											0
Closing Balance	$ 0				$ 0				$ 0	$ 0	$ 933