Components of Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Interest expense, borrowings:
Interest expense	$ 15,646	$ 15,839
Capitalized interest	(77)	(32)
Amortization of transaction costs	1,085	1,036
Interest expense resulting from derivatives	6,837	5,790
Total interest expense	$ 23,491	$ 22,633