Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized net gain on available-for-sale securities									$ (7,694)		$ (893)	$ 9,611
Unrealized net gain on cash flow hedges									(2,220,326)		(2,034,922)	(1,791,208)
Net income	95,228	47,532	53,024	55,939	138,644	76,730	64,461	59,688	251,723		339,523	352,547
Amount reclassified from Accumulated other comprehensive (loss) income, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income									3,440
Amount reclassified from Accumulated other comprehensive (loss) income, net of tax | Unrealized net gain on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized net gain on available-for-sale securities									1,317
Amount reclassified from Accumulated other comprehensive (loss) income, net of tax | Unrealized net gain on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized net gain on cash flow hedges									$ 2,123	[1]

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