Accumulated Other Comprehensive Income (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of revenue	$ (262,250)		$ (248,313)		$ (506,709)	$ (482,870)
Tax expense (benefits)	(30,421)		(28,629)		(52,504)	(43,502)
Gain (loss), net of tax	125,701	$ 102,709	108,680	$ 89,476	228,410	198,156
Accumulated Net Gain (Loss) from Cash Flow Hedges | Amount of (loss) gain reclassified from accumulated other comprehensive income into income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of revenue	2,509		(833)		3,920	(2,668)
Tax expense (benefits)	358		(379)		607	(629)
Gain (loss), net of tax	$ 2,151		$ (454)		$ 3,313	$ (2,039)