Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Rental expense	$ 64,300	$ 84,600	$ 89,900
Restructuring	72,375	67,401	98,661
Sublease income	200	200	200
GoTo Business leases for which the Company remains liable	340,034
Liability for loss on lease obligation	38,700
Purchase obligations anticipated for 2018	6,300
Contingent obligations to purchase inventory	19,400
Consolidation of leased facilities	9,718	$ 28,857	$ 22,100
Santa Clara Office
Loss Contingencies [Line Items]
Liability for loss on lease obligation	$ 34,900
Operating lease, change in price per square foot, percent	18.00%
Impact on liabilities for loss on lease obligation if price per square foot assumtion changed by $0.50	$ 5,600