Property, Plant and Equipment (Details)

6 Months Ended

Jun. 30, 2011

Fair Value of Financial Instruments

Fair Value of Financial Instruments

Note 10—Fair Value of Financial Instruments

        Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three level hierarchy has been established for valuing assets and liabilities based on how transparent (observable) the inputs are that are used to determine fair value, with the inputs considered most observable categorized as Level 1 and those that are the least observable categorized as Level 3. Hierarchy levels are defined as follows:

Level 1:	Quoted prices in active markets for identical assets and liabilities;
Level 2:	Quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and
Level 3:	Unobservable inputs that are supported by little or no market data which require the reporting entity to develop its own assumptions.

        The following table presents information about the Company's assets and liabilities that are measured at fair value on a recurring basis as of June 30, 2011 and indicate the fair value hierarchy of the valuation techniques utilized to determine such value. For some assets, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. When this is the case, the asset is categorized based on the level of the most significant input to the fair value measurement. The Company's assessment of the significance of a particular input to the fair value measurement requires judgment and considers factors specific to the assets being valued.

		June 30, 2011
		Fair Value Measurements Using
								Total Fair Value
(in thousands)		Level 1		Level 2		Level 3
Assets:
	Equity securities, trading	$	55,044	$	15,016	$	—	$	70,060
	Equity securities, available-for-sale		8,306		—		—		8,306
	Natural gas hedge		—		1,523		—		1,523
Total assets		$	63,350	$	16,593	$	—	$	79,889
Liabilities:
	Call options		—		13,130		—		13,130
	Interest rate swaps		—		634		—		634
	Interest rate cap		—		2,154		—		2,154
Total liabilities		$	—	$	15,918	$	—	$	15,918

        The following methods and assumptions were used to estimate fair value for purposes of disclosure:

        Cash and cash equivalents, restricted short-term investments, receivables and accounts payable—The carrying amounts reported in the balance sheet approximate fair value.

        Investments—As of June 30, 2011 the Company held equity investments in other current assets classified as trading and available-for-sale. Changes in the fair value of trading securities are recorded in other income and determined using observable market prices. Changes in the fair value of available-for-sale securities are recorded in accumulated other comprehensive income (loss) and determined using observable market prices.

        Debt—On April 1, 2011, the Company entered into a $2.725 billion credit agreement to partially fund the acquisition of Western Coal and to pay off all outstanding loans under the 2005 Credit Agreement. See Note 4. The Company's 2011 term loan A, term loan B and revolving credit facility in the amount of $942.5 million, $1.4 billion and $20.7 million at June 30, 2011, respectively, are carried at cost. The estimated fair value of the Company's term loan A, term loan B and revolving credit facility was $938.1 million, $1.399 billion and $20.6 million at June 30, 2011, respectively, based on similar transactions and yields in an active market for similarly rated debt.

        Call options—The fair value of call options were valued based on the Black-Scholes model using current market data.

        Interest rate swaps—The fair value of interest rate swaps were determined using quoted dealer prices for similar contracts in active over-the-counter markets.

        2011 Interest rate cap—The fair value of the interest rate cap was determined using quoted dealer prices for similar contracts in active over-the-counter markets.

        Natural gas hedge—The fair value of the natural gas hedge was determined using quoted dealer prices for similar contracts in active over-the-counter markets.