Debt (Details) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2011	Mar. 31, 2011
Debt [Abstract]
Long-term debt	$ 110,000,000		$ 110,000,000
Credit facility, maximum borrowing capacity					200,000,000	150,000,000
Credit facility, permitted increase in maximum borrowing capacity					100,000,000	150,000,000
Credit facility, expiration date			November 1, 2012
Amount borrowed under the amended credit facility			129,500,000
Restriction on maximum additional borrowing outside amended credit facility	250,000,000		250,000,000
Weighted average interest rate (in hundredths)	1.80%		1.80%
Interest and fees related to the credit facility			1,400,000
Cash paid for interest amounts	$ 983,000	$ 413,000	$ 2,400,000	$ 1,000,000