Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net										$ (3,150)	$ 4,131	$ 5,730
Operating expenses										(1,814,043)	(1,771,027)	(1,969,322)
Net income		$ 283,889	$ (126,720)	$ (108,829)	$ (27,621)	$ (199,850)	$ (131,901)	$ (120,898)	$ (83,463)	20,719	$ (536,112)	$ (319,361)
Amount reclassified from Accumulated other comprehensive loss, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income										(1,031)
Amount reclassified from Accumulated other comprehensive loss, net of tax | Unrealized net losses on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net										(273)
Amount reclassified from Accumulated other comprehensive loss, net of tax | Unrealized net gains on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating expenses	[1]									$ (758)

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