Derivatives (Effect of Interest Rate Contracts on the Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
The effect of interest rate contracts on the statement of operations:
Loss recognized in income on interest rate contracts	$ 3,334	$ 3,638	$ 6,700	$ 7,279
(Gain) loss recognized in AOCI on interest rate contracts (effective portion)			(4,605)	(5,837)
Loss reclassified from AOCI into income (effective portion)			6,621	7,298
(Gain) loss recognized in income on interest rate contracts (ineffective portion and amount excluded from effectiveness testing)			$ 79	$ (19)