Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Thousands	Jun. 30, 2011		Jun. 30, 2010	Mar. 31, 2010
Assets	$ 2,900		$ 62,500	$ 28,200
Total net liability	1,314,591	[1]
Long-term debt, Fair Value	1,304,590
Long-term debt, Carrying Value	1,261,766
Interest Rate Swap [Member]
Liabilities	1,157	[1]
Interest Rate Swap [Member] | Level 1[Member]
Liabilities	0	[1]
Interest Rate Swap [Member] | Level 2 [Member]
Liabilities	1,157	[1],[2]
Interest Rate Swap [Member] | Level 3 [Member]
Liabilities	0	[1]
Oil and Gas Swaps and Collars [Member]
Assets	7,531	[1]
Liabilities	16,680	[1]
Oil and Gas Swaps and Collars [Member] | Level 1[Member]
Assets	0	[1]
Liabilities	0	[1]
Oil and Gas Swaps and Collars [Member] | Level 2 [Member]
Assets	7,531	[1],[2]
Liabilities	16,680	[1],[2]
Oil and Gas Swaps and Collars [Member] | Level 3 [Member]
Assets	0	[1]
Liabilities	0	[1]
Foreign Currency Forwards [Member]
Assets	305
Foreign Currency Forwards [Member] | Level 1[Member]
Assets	0
Foreign Currency Forwards [Member] | Level 2 [Member]
Assets	305	[2]
Foreign Currency Forwards [Member] | Level 3 [Member]
Assets	0
Fair Value of Long Term Debt [Member]
Liabilities	1,304,590	[3]
Fair Value of Long Term Debt [Member] | Level 1[Member]
Liabilities	1,182,173	[3]
Fair Value of Long Term Debt [Member] | Level 2 [Member]
Liabilities	122,417	[2],[3]
Fair Value of Long Term Debt [Member] | Level 3 [Member]
Liabilities	0	[3]
Level 1[Member]
Total net liability	1,182,173	[1]
Level 2 [Member]
Total net liability	132,418	[1],[2]
Level 3 [Member]
Total net liability	$ 0	[1]

[1] Income Approach. Techniques to convert expected future cash flows to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).

[2] Unless otherwise indicated, the fair value of our Level 2 derivative instruments reflects our best estimate and is based upon exchange or over-the-counter quotations whenever they are available. Quoted valuations may not be available due to location differences or terms that extend beyond the period for which quotations are available. Where quotes are not available, we utilize other valuation techniques or models to estimate market values. These modeling techniques require us to make estimations of future prices, price correlation and market volatility and liquidity. Our actual results may differ from our estimates, and these differences can be positive or negative.

[3] We have elected not to record our debt at fair value in the accompanying condensed consolidated balance sheets. See Note 7 for additional information regarding our long term debt. The fair value of our long term debt at June 30, 2011 is as follows: