Components of Interest Expense (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
Interest expense, borrowings:
Interest expense	$ 16,540	$ 16,009	$ 48,715	$ 47,888
Capitalized interest	(119)	(76)	(290)	(154)
Amortization of transaction costs	1,014	1,198	3,149	3,292
Interest expense resulting from derivatives	4,641	5,613	16,106	17,314
Total interest expense	$ 22,076	$ 22,744	$ 67,680	$ 68,340