Investments (Details Textuals) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investments, Debt and Equity Securities [Abstract]
Marketable securities	$ 35,500,000	$ 0	$ 0
Held-to-maturity Securities	4,800,000	0
Investments (Textuals) [Abstract]
Proceeds from Sale of Available-for-sale Securities	17,200,000	52,800,000
Realized gains from sale of available-for-sale securities	100,000	1,600,000
Proceeds from Sale and Maturity of Marketable Securities	46,400,000	104,600,000	12,400,000
Newcastle Coal Infrastructure Group [Domain]
Investments (Textuals) [Abstract]
Fair Value of securities	0
Realized losses from sale of available-for-sale securities	200,000
Proceeds from Sale and Maturity of Marketable Securities	$ 29,200,000

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

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+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References+ Details

- Definition

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

+ References

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+ Details

- Definition

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

+ References

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