Additional interest income under a full accrual basis

No definition available.

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- Definition

Business Acquisition, Percentage of Undivided Interests Acquired

+ References

No definition available.

+ Details

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- Definition

Percentage of Agreed Sale Price as Final Installment Payment

+ References

No definition available.

+ Details

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- Definition

Sale of Business, Percentage of Ownership Before Transaction

+ References

No definition available.

+ Details

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- Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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- Definition

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.7(b))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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- Definition

Aggregate carrying amount, as of the balance sheet date, of investments and other noncurrent assets not separately disclosed in the balance sheet due to materiality considerations. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

+ References

No definition available.

+ Details

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- Details

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- Details

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Financing Receivables (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2011	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 2.5us-gaap_InvestmentIncomeInterest	$ 3.6us-gaap_InvestmentIncomeInterest
Middlemount Mine [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity method investment, ownership percentage	50.00%
Basis spread over Australian Bank Bill Swap Reference Rate	3.50%
Interest income	0.6	1.4
Additional interest income under a full accrual basis	1.5	1.7
Codrilla Mine Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of ownership before selldown			85.00%
Percentage of agreed sale price as final installment payment due	40.00%
Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investments and other assets	323.5			347.2
Financing Receivable [Member] \| Middlemount Mine [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investments and other assets	297.5			319.6
Financing Receivable [Member] \| Codrilla Mine Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investments and other assets	$ 26.0			$ 27.6
Coppabella, Moorvale, and Codrilla Mines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of undivided interests acquired			73.30%