Components of Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest expense, borrowings:
Interest expense	$ 18,055	$ 16,529	$ 35,869	$ 32,175
Capitalized interest	(128)	(94)	(270)	(171)
Amortization of transaction costs	843	1,050	1,694	2,135
Interest expense resulting from derivatives	4,348	4,628	9,153	11,465
Total interest expense	$ 23,118	$ 22,113	$ 46,446	$ 45,604