Restructuring Charges (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) employee	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	$ 3,644	$ 26,232	$ 16,923
Contract Termination
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	1,400
Contract Termination | Accrued Liabilities
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	$ 700
2014 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of employees impacted | employee	290
Total Incurred and Anticipated Charges	$ 26,615
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	16,352	0
Restructuring charges	2,148	24,467
Non-cash items	(205)	(297)
Cash paid	(14,643)	(7,528)
Foreign exchange rate changes	(871)	(290)
Restructuring liability at the end of period	2,781	16,352	0
2014 Restructuring Plan | North America
Restructuring Cost and Reserve [Line Items]
Total Incurred and Anticipated Charges	1,044
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	33
2014 Restructuring Plan | International
Restructuring Cost and Reserve [Line Items]
Total Incurred and Anticipated Charges	18,207
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	376
2014 Restructuring Plan | Other
Restructuring Cost and Reserve [Line Items]
Total Incurred and Anticipated Charges	399
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	85
2014 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Total Incurred and Anticipated Charges	6,965
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	1,654
2014 Restructuring Plan | Employee Severance and Termination
Restructuring Cost and Reserve [Line Items]
Total Incurred and Anticipated Charges	20,000
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	15,152	0
Restructuring charges	576	19,292
Non-cash items	(205)	(220)
Cash paid	(12,861)	(3,630)
Foreign exchange rate changes	(871)	(290)
Restructuring liability at the end of period	1,791	15,152	0
2014 Restructuring Plan | Professional Fees, Office Closures and Other
Restructuring Cost and Reserve [Line Items]
Total Incurred and Anticipated Charges	7,000
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	1,200	0
Restructuring charges	1,572	5,175
Non-cash items	0	(77)
Cash paid	(1,782)	(3,898)
Foreign exchange rate changes	0	0
Restructuring liability at the end of period	$ 990	1,200	0
2013 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of employees impacted | employee	250
Plan to Date	$ 12,720
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	0	7,454	0
Restructuring charges		(701)	13,421
Non-cash items		17	(137)
Cash paid		(6,677)	(5,990)
Foreign exchange rate changes		(93)	160
Restructuring liability at the end of period		0	7,454	$ 0
2013 Restructuring Plan | North America
Restructuring Cost and Reserve [Line Items]
Plan to Date	548
2013 Restructuring Plan | International
Restructuring Cost and Reserve [Line Items]
Plan to Date	11,394
2013 Restructuring Plan | Other
Restructuring Cost and Reserve [Line Items]
Plan to Date	57
2013 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Plan to Date	721
2012 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Plan to Date	14,048
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	1,694	2,770	5,088	0
Restructuring charges	99	2,466	3,502	7,981
Non-cash items	(1)	0	510	(675)
Cash paid	(1,781)	(3,532)	(6,272)	(2,218)
Foreign exchange rate changes	(11)	(10)	(58)
Restructuring liability at the end of period	0	1,694	2,770	5,088
2012 Restructuring Plan | North America
Restructuring Cost and Reserve [Line Items]
Plan to Date	1,690
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	(12)
2012 Restructuring Plan | International
Restructuring Cost and Reserve [Line Items]
Plan to Date	8,851
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	0
2012 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Plan to Date	3,507
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring charges	111
2012 Restructuring Plan | Employee Severance and Termination
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	0	0	3,556	0
Restructuring charges	0	0	370	6,517
Non-cash items	0	0	0	(743)
Cash paid	0	0	(3,851)	(2,218)
Foreign exchange rate changes	0	0	(75)
Restructuring liability at the end of period	0	0	0	3,556
2012 Restructuring Plan | Office Closures
Changes in restructuring liabilities, recorded in other accrued expenses
Restructuring liability at the beginning of period	1,694	2,770	1,532	0
Restructuring charges	99	2,466	3,132	1,464
Non-cash items	(1)	0	510	68
Cash paid	(1,781)	(3,532)	(2,421)	0
Foreign exchange rate changes	(11)	(10)	17
Restructuring liability at the end of period	$ 0	$ 1,694	$ 2,770	$ 1,532