Accumulated Other Comprehensive Income (Schedule of Reclassifications out of Accumulated Other Comprehensive Income) (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 on Derivatives [Line Items]
Cost of revenue	$ 248,313	$ 216,225	$ 482,870	$ 420,055
Tax (benefits) expense	28,629	29,178	43,502	44,857
Net income	108,680	85,407	198,156	154,465
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest | Amount of (loss) gain reclassified from accumulated other comprehensive income into income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Tax (benefits) expense	(379)	280	(629)	681
Net income	(454)	473	(2,039)	1,147
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest | Foreign currency exchange contracts | 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	$ (833)	$ 753	$ (2,668)	$ 1,828