v2.4.1.9

COMMITMENTS AND CONTINGENCIES (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2013
Marketing Agreements
Period of cancellation of marketing agreement by way of written notice	30 days
Reclamation Deposits and Surety Bonds
Security placed with the State of Utah and BLM	$ 18.0ipi_ReclamationDepositsAndSuretyBonds
Long-term restricted cash deposits	0.5us-gaap_RestrictedCashAndCashEquivalentsNoncurrent
Surety bonds issued by an insurer	17.5ipi_SuretyBonds
New Mexico Employment Credits
Tax Credit Receivable		5.9ipi_TaxCreditReceivable
Other Cost and Expense, Operating		2.9us-gaap_OtherCostAndExpenseOperating
Other Receivables	2.0us-gaap_OtherReceivables
Allowance for doubtful other receivables, current	$ 0.7us-gaap_AllowanceForDoubtfulOtherReceivablesCurrent		$ 2.8us-gaap_AllowanceForDoubtfulOtherReceivablesCurrent
Future Operating Lease Commitments
Operating Lease, Contract Term, Maximum (in years)	20 years

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- Definition

Operating Lease, Contract Term, Maximum

+ References

No definition available.

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- Definition

Represents the period of time for which written notice is required to be given prior to cancellation of the marketing agreement.

+ References

No definition available.

+ Details

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- Definition

Represents the value of reclamation deposits and surety bonds as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Represents the value of surety bonds secured by an insurer as of the balance sheet date.

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

Receivable for New Mexico High Wage Jobs Credit

+ References

No definition available.

+ Details

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- Definition

A valuation allowance for doubtful other receivables due to an entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible and not separately disclosed.

+ References

No definition available.

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- Definition

The total amount of other operating cost and expense items that are associated with the entity's normal revenue producing operation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.3)

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Carrying amounts due as of the balance sheet date from parties or arising from transactions not otherwise specified in the taxonomy.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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- Definition

Cash and equivalents whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5



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

-Publisher FASB

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-Subparagraph (SX 210.5-02.1)

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

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