Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net										$ 8,373	$ (3,150)	$ 4,131
Operating expenses										(1,862,140)	(1,814,043)	(1,771,027)
Net income		$ (165,718)	$ (158,857)	$ (106,833)	$ (144,259)	$ 283,889	$ (126,720)	$ (108,829)	$ (27,621)	(575,667)	$ 20,719	$ (536,112)
Amount reclassified from Accumulated other comprehensive loss, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income										6,695
Amount reclassified from Accumulated other comprehensive loss, net of tax | Unrealized net loss on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net										5,996
Amount reclassified from Accumulated other comprehensive loss, net of tax | Unrealized net loss on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating expenses	[1]									$ 699

[1] Operating expenses amounts allocated to Research and development, Sales, marketing and services, and General and administrative are not individually significant.