Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012
Total net liability	$ 1,266,252
Level 1 [Member]
Total net liability	1,143,077
Level 2 [Member]
Total net liability	123,175	[1]
Level 3 [Member]
Total net liability
Natural Gas Contracts [Member]
Assets	20,239
Natural Gas Contracts [Member] | Level 1 [Member]
Assets
Natural Gas Contracts [Member] | Level 2 [Member]
Assets	20,239	[1]
Natural Gas Contracts [Member] | Level 3 [Member]
Assets
Foreign Currency Forwards [Member]
Assets	110
Foreign Currency Forwards [Member] | Level 1 [Member]
Assets
Foreign Currency Forwards [Member] | Level 2 [Member]
Assets	110	[1]
Foreign Currency Forwards [Member] | Level 3 [Member]
Assets
Interest Rate Swaps [Member]
Assets	83
Interest Rate Swaps [Member] | Level 1 [Member]
Assets
Interest Rate Swaps [Member] | Level 2 [Member]
Assets	83	[1]
Interest Rate Swaps [Member] | Level 3 [Member]
Assets
Oil Contracts [Member]
Liabilities	23,647	[2]
Oil Contracts [Member] | Level 1 [Member]
Liabilities		[2]
Oil Contracts [Member] | Level 2 [Member]
Liabilities	23,647	[1],[2]
Oil Contracts [Member] | Level 3 [Member]
Liabilities		[2]
Fair Value Of Long Term Debt [Member]
Liabilities	1,262,686
Fair Value Of Long Term Debt [Member] | Level 1 [Member]
Liabilities	1,143,077
Fair Value Of Long Term Debt [Member] | Level 2 [Member]
Liabilities	119,609	[1]
Fair Value Of Long Term Debt [Member] | Level 3 [Member]
Liabilities
Interest Rate Swaps [Member]
Liabilities	338
Interest Rate Swaps [Member] | Level 1 [Member]
Liabilities
Interest Rate Swaps [Member] | Level 2 [Member]
Liabilities	338	[1]
Interest Rate Swaps [Member] | Level 3 [Member]
Liabilities
Foreign Currency Forwards [Member]
Liabilities	13
Foreign Currency Forwards [Member] | Level 1 [Member]
Liabilities
Foreign Currency Forwards [Member] | Level 2 [Member]
Liabilities	13	[1]
Foreign Currency Forwards [Member] | Level 3 [Member]
Liabilities

[1] 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 could be positive or negative.

[2] See Note 7 for additional information regarding our long term debt. The fair value of our long term debt at March 31, 2012 is as follows:Fair Value Carrying ValueTerm Loans (mature July 2015)  $380,395  $379,000Revolving Credit Facility (matures July 2015)  100,000100,0002025 Notes (mature March 2025) 160,099157,830(a)2032 Notes (mature March 2032)212,500200,000(b)Senior Unsecured Notes (mature January 2016) 290,083274,960MARAD Debt (matures February 2027) (c) 119,609107,756  Total $1,262,686$1,219,546Amount excludes the related unamortized debt discount of $3.7 million. Amount excludes the related unamortized debt discount of $35.4 million.The estimated fair value of all debt, other than the MARAD debt, was determined using Level 1 inputs using the market approach. The fair value of the MARAD debt was determined using a third party evaluation of the remaining average life and outstanding principal balance of the MARAD indebtedness as compared to other governmental obligations in the marketplace with similar terms. The fair value of the MARAD Debt was estimated using Level 2 fair value inputs using the market approach.