Acquisition Integration and Restructuring (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended						12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Restructuring Cost and Reserve [Line Items]
Remaining restructuring reserve	$ 3,719						$ 3,719
Restructuring reserve included in accrued expenses	3,155						3,155	3,814
Restructuring reserve included in other long term liabilities	564						564	1,941
Summary of cost reduction and restructuring actions [Roll Forward]
Restructuring and cost reduction related cost							2,052	5,307	1,050
Impairment charges and other relocation expenses								246	388
Reserve reversed due to office consolidation							40	494
Consulting and moving fees related to restructuring								197
Legal fees related to restructuring activities							19
Total expense of acquisition integration costs and interest expense							2,031
Restructuring charges	546	[1]	674	311	1,218	2,416	1,774	5,256	1,438
Interest expense	1,021	[1]	1,073	1,135	917	917	4,324	3,652	5,270
Expenses related to cost reduction program [Abstract]
Period ended							1,774	5,256	1,438	2,114	6,243	10,149
Cumulative since program inception							26,974
Americas [Member]
Expenses related to cost reduction program [Abstract]
Period ended							1,376	4,245	777	1,136	3,398	5,460
Cumulative since program inception							16,392
Europe [Member]
Expenses related to cost reduction program [Abstract]
Period ended							293	881	586	555	1,400	3,552
Cumulative since program inception							7,267
Asia Pacific [Member]
Expenses related to cost reduction program [Abstract]
Period ended							104	129	0	(70)	992	248
Cumulative since program inception							1,403
Corporate [Member]
Expenses related to cost reduction program [Abstract]
Period ended							1	1	75	493	453	889
Cumulative since program inception							1,912
Actions Initiated in 2008 [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							2,761	2,789	3,510
New accruals							0	0	0
Adjustments							346	562	112
Cash payments							(850)	(590)	(833)
End of Period	2,257						2,257	2,761	2,789
Actions Initiated in 2008 [Member] | Employee Terminations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0	0	142
New accruals							0	0	0
Adjustments							0	0	4
Cash payments							0	0	(146)
End of Period	0						0	0	0
Actions Initiated in 2008 [Member] | Lease Obligations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							2,761	2,789	3,368
New accruals							0	0	0
Adjustments							346	562	108
Cash payments							(850)	(590)	(687)
End of Period	2,257						2,257	2,761	2,789
Actions Initiated in 2009 [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0	0	104
New accruals							0	0	21
Adjustments							0	0	(1)
Cash payments							0	0	(124)
End of Period	0						0	0	0
Actions Initiated in 2009 [Member] | Employee Terminations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0	0	104
New accruals							0	0	21
Adjustments							0	0	(1)
Cash payments							0	0	(124)
End of Period	0						0	0	0
Actions Initiated in 2009 [Member] | Lease Obligations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0	0	0
New accruals							0	0	0
Adjustments							0	0	0
Cash payments							0	0	0
End of Period	0						0	0	0
Actions Initiated in 2010 [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							402	408	570
New accruals							0	10	13
Adjustments							(8)	8	(37)
Cash payments							(394)	(24)	(138)
End of Period	0						0	402	408
Actions Initiated in 2010 [Member] | Employee Terminations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							402	408	570
New accruals							0	10	13
Adjustments							(8)	8	(37)
Cash payments							(394)	(24)	(138)
End of Period	0						0	402	408
Actions Initiated in 2010 [Member] | Lease Obligations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0	0	0
New accruals							0	0	0
Adjustments							0	0	0
Cash payments							0	0	0
End of Period	0						0	0	0
Actions Initiated in 2011 [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							15	125	0
New accruals							0	0	957
Adjustments							(15)	(7)	(15)
Cash payments							0	(103)	(817)
End of Period	0						0	15	125
Actions Initiated in 2011 [Member] | Employee Terminations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							15	125	0
New accruals							0	0	957
Adjustments							(15)	(7)	(15)
Cash payments							0	(103)	(817)
End of Period	0						0	15	125
Actions Initiated in 2011 [Member] | Lease Obligations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0	0	0
New accruals							0	0	0
Adjustments							0	0	0
Cash payments							0	0	0
End of Period	0						0	0	0
Actions Initiated In 2012 [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							2,573	0
New accruals							50	4,541
Adjustments							151	193
Cash payments							(2,091)	(2,161)
End of Period	683						683	2,573
Actions Initiated In 2012 [Member] | Employee Terminations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							1,386	0
New accruals							50	3,006
Adjustments							(63)	(26)
Cash payments							(1,347)	(1,594)
End of Period	26						26	1,386
Actions Initiated In 2012 [Member] | Lease Obligations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							1,187	0
New accruals							0	1,535
Adjustments							214	219
Cash payments							(744)	(567)
End of Period	657						657	1,187
Actions Initiated In 2013 [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0
New accruals							1,528
Adjustments							0
Cash payments							(749)
End of Period	779						779
Actions Initiated In 2013 [Member] | Employee Terminations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0
New accruals							1,144
Adjustments							0
Cash payments							(669)
End of Period	475						475
Actions Initiated In 2013 [Member] | Lease Obligations [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Beginning of Period							0
New accruals							384
Adjustments							0
Cash payments							(80)
End of Period	304						304
Acquisition integration and restructuring expenses [Member]
Summary of cost reduction and restructuring actions [Roll Forward]
Interest expense							$ 257

[1] Results for the fourth quarter of 2013 were favorably impacted by a credit to income of approximately $518 for the reversal of a liability recorded in purchase accounting for a recent acquisition that is no longer needed due to statute expiration in the current quarter, and a credit to income of approximately $425 for net reserve reductions at certain of the Company’s vacant leased properties, for which a change in circumstances in the current quarter required a revision in the estimate of future expenses related to the leases. In addition, results for the current quarter were favorably impacted by a credit to income of approximately $736 for the correction of an error in the valuation of unbilled services that was immaterial to all prior periods presented.