Effect of Interest Rate Contracts on the Statement of Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
The Effect of Interest Rate Contracts on the Statements of Operations
Interest expense resulting from derivatives	$ 4,641	$ 5,613	$ 16,106	$ 17,314
(Gain) loss recognized in AOCI on interest rate contracts (effective portion)			(4,501)	13,133
(Gain) loss reclassified from AOCI into income (effective portion)			14,828	17,984
(Gain) loss recognized in income on interest rate contracts (ineffective portion and amount excluded from effectiveness testing)			$ 1,277	$ (670)