Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other (expense) income, net		$ 2,537	$ 1,141	$ 5,549	$ (2,185)
Operating expenses		488,469	461,974	911,812	899,549
Net income		(106,833)	$ (108,829)	(251,092)	$ (136,450)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income		(754)		(972)
Unrealized Net Losses on Available-for-sale Securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other (expense) income, net		243		1,244
Unrealized Net Gains on Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating expenses	[1]	$ (997)		$ (2,216)

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