Restructuring - (Restructuring Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 16,725	$ 72,375	$ 67,401
Operational Initiatives for Cloud-based Subscription Business, Strategic Focus and Efficiencies
Restructuring Cost and Reserve [Line Items]
Restructuring	2,500	53,700	0
Operational Initiatives for Infrastructure Scalability and Cost Saving Efficiencies
Restructuring Cost and Reserve [Line Items]
Restructuring		8,100	0
November 2015 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring		1,900	44,500
January 2015 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring		$ 8,700	$ 24,000
Consolidation of Leased Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 14,200