Accumulated Other Comprehensive Income (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of revenue	$ (244,459)	$ (234,557)
Tax expense (benefits)	(22,083)	(14,873)
Net income	102,709	89,476
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	1,411	(1,835)
Tax expense (benefits)	249	(250)
Net income	$ 1,162	$ (1,585)