Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		15 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred		$ 49,300		$ 13,400		$ 62,700
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018				14,243
Costs incurred	$ 266		$ 2,971	15,174	$ 2,971
Cash disbursements				(22,608)
Software and other non-cash charges				(4,605)
Translation adjustments and other				(181)
Balance as of June 30, 2018	2,023	14,243		2,023
Employee Severance and Related Benefits
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018				12,857
Costs incurred				6,761
Cash disbursements				(17,831)
Software and other non-cash charges				0
Translation adjustments and other				0
Balance as of June 30, 2018	1,787	12,857		1,787
Software Charges
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018				0
Costs incurred				2,818
Cash disbursements				0
Software and other non-cash charges				(2,818)
Translation adjustments and other				0
Balance as of June 30, 2018	0	0		0
Excess Facilities, Contract Terminations and Other
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018				1,386
Costs incurred				5,595
Cash disbursements				(4,777)
Software and other non-cash charges				(1,787)
Translation adjustments and other				(181)
Balance as of June 30, 2018	$ 236	$ 1,386		$ 236