number of mining complexes temporarily idled

No definition available.

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Balance Type:	na
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- Definition

Net amount of current deferred finance costs capitalized at the end of the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.8)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 8

-Article 5

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

For an unclassified balance sheet, the carrying amount (net of accumulated amortization) as of the balance sheet date of capitalized costs associated with the issuance of debt instruments (for example, legal, accounting, underwriting, printing, and registration costs) that will be charged against earnings over the life of the debt instruments to which such costs pertain.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest capitalized during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Allowance for Funds Used during Construction

-URI http://asc.fasb.org/extlink&oid=6504829

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount at the balance sheet date of mineral rights, or rights to extract a mineral from the earth or to receive payment in the form of a royalty for the extraction of minerals, net of amortization.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Mineral Rights

-URI http://asc.fasb.org/extlink&oid=6919630

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Details

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Namespace Prefix:
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Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
Accounting Policies (Narrative) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statutory Accounting Practices
Interest Costs Capitalized		$ 15,900,000us-gaap_InterestCostsCapitalized	$ 15,600,000us-gaap_InterestCostsCapitalized
Mineral Rights	4,700,000,000us-gaap_MineralRights	4,800,000,000us-gaap_MineralRights
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	265,600,000
Unrecorded Unconditional Purchase Obligation, Due within Two Years	118,100,000
Deferred Finance Costs, Net	89,066,000us-gaap_DeferredFinanceCostsNet	99,185,000us-gaap_DeferredFinanceCostsNet
Deferred Finance Costs, Current, Net	25,500,000us-gaap_DeferredFinanceCostsCurrentNet	19,700,000us-gaap_DeferredFinanceCostsCurrentNet
number of mining complexes temporarily idled	1
Exploration and Production Equipment [Member] \| Minimum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	5 years
Exploration and Production Equipment [Member] \| Maximum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	32 years
Building and Building Improvements [Member] \| Minimum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	10 years
Building and Building Improvements [Member] \| Maximum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	30 years
Mining Properties and Mineral Rights [Member] \| Minimum [Member]
Statutory Accounting Practices
Lessee Leasing Arrangements, Operating Leases, Term of Contract	10 years
Mining Properties and Mineral Rights [Member] \| Maximum [Member]
Statutory Accounting Practices
Lessee Leasing Arrangements, Operating Leases, Term of Contract	50 years
Capital Addition Purchase Commitments [Member]
Statutory Accounting Practices
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	75,400,000
Unrecorded Unconditional Purchase Obligation, Due within Two Years	$ 60,000,000