Foreign Currency Exchange Contracts and Hedging (Narrative) (Details) - Foreign currency exchange contracts $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Nov. 09, 2016 USD ($) counterparty	Sep. 30, 2016 USD ($) counterparty	Sep. 30, 2016 USD ($) counterparty	Sep. 30, 2015 USD ($)
Derivatives designated as cash flow hedges
Summary of the effect of derivative instruments on the consolidated statements of income
Amount of gain (loss) recognized in other comprehensive income on derivatives (effective portion)			$ 4,903	$ (1,498)
Amount of gain (loss) reclassified from accumulated other comprehensive income into income (effective portion)			1,676	(794)
Amount of gain excluded from effectiveness testing			355	66
Designated as hedging instrument
Foreign currency exchange contracts and hedging
Derivative notional amount		$ 71,000	$ 71,000
Number of counterparties in derivative contracts | counterparty		7	7
Remaining maturity of foreign currency derivatives (in months)			6 months
Derivative, settled during period, notional amount		$ 41,000	$ 44,000
Non-designated derivatives
Foreign currency exchange contracts and hedging
Derivative notional amount		$ 30,000	$ 30,000
Number of counterparties in derivative contracts | counterparty		4	4
Remaining maturity of foreign currency derivatives (in months)			6 months
Derivative, entered into and settled during period, notional amount		$ 61,000	$ 124,000
Summary of the effect of derivative instruments on the consolidated statements of income
Amount of loss recognized in income on derivatives			$ (881)	$ (461)
Non-designated derivatives | Subsequent event
Foreign currency exchange contracts and hedging
Derivative notional amount	$ 48,000
Number of counterparties in derivative contracts | counterparty	9
Remaining maturity of foreign currency derivatives (in months)	3 months