Restructuring Charges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	$ 1,508		$ 604	$ 1,406		$ 953
2013 Plan
Restructuring Charges
Expected number of employees to be impacted by the restructuring				250
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability, as of January 1, 2014				7,454
Restructuring credit	(62)			(475)
Non-cash items				17
Cash paid				(5,996)
Foreign exchange rate changes				(69)
Restructuring liability, as of June 30, 2014	931			931
Restructuring charges, incurred to date				12,946
2013 Plan | North America
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	(52)			(112)
Restructuring charges, incurred to date				548
2013 Plan | International
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	(31)			(496)
Restructuring charges, incurred to date				11,620
2013 Plan | Other
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	0			(7)
Restructuring charges, incurred to date				57
2013 Plan | Corporate
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	21			140
Restructuring charges, incurred to date				721
2012 Plan
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	1,570			1,881
Restructuring charges, incurred to date				13,364	[1]
2012 Plan | North America
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	10			33
Restructuring charges, incurred to date				1,738	[1]
2012 Plan | International
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	596			856
Restructuring charges, incurred to date				7,936	[1]
2012 Plan | Corporate
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring credit	964	[2]		992	[2]
Restructuring charges, incurred to date				3,690	[1],[2]
2012 Plan | Office Closures
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability, as of January 1, 2014				2,770
Restructuring credit				1,881
Cash paid				(1,713)
Foreign exchange rate changes				5
Restructuring liability, as of June 30, 2014	$ 2,943			$ 2,943

[1] Our restructuring charges, particularly lease-related office closure costs, are subject to estimate. If we are unable to find tenants for vacated offices or sub-lease terms are different from our assumptions, our actual restructuring charges will differ from our current estimates.

[2] Corporate restructuring charges include costs for administrative facility consolidation.