Restructuring Charges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				$ 6,950				$ 7,996	$ 6,950	$ 7,996	$ 11,655
Restructuring charges	1,431	608	678	2,225	2,232	75	1,206	269	4,942	3,782	4,222
Restructuring liabilities									(4,694)	(3,888)	(6,718)
Adjustment to liability									24	(954)	(1,150)
Foreign currency translation adjustment									2	14	(13)
Closing Balance	7,224				6,950				7,224	6,950	7,996
Marketing & Events Group [Member]
Reconciliation of beginning and ending liability balances by major restructuring activity
Restructuring charges									3,479	3,756	3,232
Marketing & Events Group [Member] | Severance & Employee Benefits [Member]
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				831				1,106	831	1,106	2,333
Restructuring charges									2,506	1,182	2,637
Restructuring liabilities									(2,670)	(1,175)	(3,387)
Adjustment to liability									51	(294)	(466)
Foreign currency translation adjustment									2	12	(11)
Closing Balance	720				831				720	831	1,106
Marketing & Events Group [Member] | Facilities [Member]
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				4,819				5,051	4,819	5,051	6,295
Restructuring charges									2,346	2,519	1,180
Restructuring liabilities									(1,567)	(2,356)	(2,164)
Adjustment to liability									(27)	(397)	(258)
Foreign currency translation adjustment										2	(2)
Closing Balance	5,571				4,819				5,571	4,819	5,051
Other Restructuring [Member] | Severance & Employee Benefits [Member]
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				24				197	24	197
Restructuring charges									90	26	542
Restructuring liabilities									(114)	(199)	(292)
Adjustment to liability											(53)
Foreign currency translation adjustment
Closing Balance					24					24	197
Other Restructuring [Member] | Facilities [Member]
Reconciliation of beginning and ending liability balances by major restructuring activity
Beginning Balance				1,276				1,642	1,276	1,642	3,027
Restructuring charges										55	(137)
Restructuring liabilities									(343)	(158)	(875)
Adjustment to liability										(263)	(373)
Foreign currency translation adjustment
Closing Balance	$ 933				$ 1,276				$ 933	$ 1,276	$ 1,642