Restructuring Restructuring Costs (Details) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2017 USD ($) employee		Jun. 30, 2016 USD ($) employee		Jun. 30, 2017 USD ($) employee		Jun. 30, 2016 USD ($) employee
Restructuring Cost and Reserve [Line Items]
Revenue		$ 662,619		$ 723,760		$ 1,336,245		$ 1,422,195
Restructuring Charges		$ 4,584		$ 15,702		$ 7,315		$ 27,215
Restructuring and Related Cost, Number of Positions Eliminated | employee		150		250		350		550
North America [Member]
Restructuring Cost and Reserve [Line Items]
Revenue	[1]	$ 451,912		$ 516,922		$ 925,269		$ 1,017,735
Restructuring Charges		2,975		2,806		4,930		8,425
EMEA [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1,609		12,896		2,385		18,790
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs						68,700
Restructuring Charges		2,773	[2]	14,053	[3]	5,074	[4]	24,378	[5]
Employee Severance [Member] | North America [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		2,687		1,488		4,465		6,213
Employee Severance [Member] | EMEA [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		86		12,565		609		18,165
Asset Impairments Related to Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs						7,500
Restructuring Charges		0		0		0		45
Asset Impairments Related to Restructuring [Member] | North America [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0		0		0		45
Asset Impairments Related to Restructuring [Member] | EMEA [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0		0		0		0
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1,811		1,649		2,241		2,792
Other Restructuring [Member] | North America [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		288		1,318		465		2,167
Other Restructuring [Member] | EMEA [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		$ 1,523		$ 331		$ 1,776		$ 625
Facility Closing [Member] | ROW [Member]
Restructuring Cost and Reserve [Line Items]
Number of Countries in which Entity Operates		17				17

[1] North America includes revenue from the United States of $442.7 million and $508.8 million for the three months ended June 30, 2017 and 2016, respectively, and $907.4 million and $1,001.4 million for the six months ended June 30, 2017 and 2016, respectively. International includes revenue from the United Kingdom of $74.4 million and $78.4 million for the three months ended June 30, 2017 and 2016, respectively, and $139.9 million and $152.4 million for the six months ended June 30, 2017 and 2016, respectively. There were no other individual countries that represented more than 10% of consolidated total revenue for the three and six months ended June 30, 2017 and 2016. In prior periods, revenue was attributed to individual countries based on the domicile of the legal entities within the Company's consolidated group that undertook those transactions. The Company updated its attribution of revenue by country in the current period to be based on the location of the customer. Prior period revenue amounts by country have been retrospectively adjusted to reflect that change in attribution.

[2] (1)The employee severance and benefit costs for the three months ended June 30, 2017 relates to the termination of approximately 150 employees. Substantially all of the remaining cash payments for those costs are expected to be disbursed through December 31, 2017.

[3] The employee severance and benefit costs for the three months ended June 30, 2016 related to the termination of approximately 250 employees.

[4] The employee severance and benefit costs for the six months ended June 30, 2017 relates to the termination of approximately 350 employees. Substantially all of the remaining cash payments for those costs are expected to be disbursed through December 31, 2017.

[5] (1)The employee severance and benefit costs for the six months ended June 30, 2016 related to the termination of approximately 550 employees.