Restructuring - (Restructuring Charges by Segment) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring	[1]	$ 71,122	$ 100,411	$ 20,424
Enterprise and Service Provider
Restructuring Cost and Reserve [Line Items]
Restructuring		67,401	96,952	14,092
GoTo Business
Restructuring Cost and Reserve [Line Items]
Restructuring		$ 3,721	$ 3,459	$ 6,332

[1] Represents expenses presented to management on a consolidated basis only and not allocated to the operating segments.