Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended			15 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 13,100	$ 49,300		$ 62,400
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	14,243
Costs incurred	14,908		$ 0
Cash disbursements	(13,752)
Software and other non-cash charges	(4,605)
Balance as of March 31, 2018	10,794	14,243		10,794
Employee Severance and Related Benefits
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	12,857
Costs incurred	7,163
Cash disbursements	(10,766)
Software and other non-cash charges	0
Balance as of March 31, 2018	9,254	12,857		9,254
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)
Balance as of March 31, 2018	0	0		0
Excess Facilities, Contract Terminations and Other
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	1,386
Costs incurred	4,927
Cash disbursements	(2,986)
Software and other non-cash charges	(1,787)
Balance as of March 31, 2018	$ 1,540	$ 1,386		$ 1,540