v2.4.1.9

CASH, CASH EQUIVALENTS, AND INVESTMENTS (Summary of Cash, Cash Equivalents, and Investments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Cash and cash equivalents	$ 66,786us-gaap_CashAndCashEquivalentsAtCarryingValue	$ 67,589us-gaap_CashAndCashEquivalentsAtCarryingValue	$ 3,234us-gaap_CashAndCashEquivalentsAtCarryingValue	$ 394us-gaap_CashAndCashEquivalentsAtCarryingValue
Short-term investments	34,310us-gaap_ShortTermInvestments	10,434us-gaap_ShortTermInvestments
Long-term investments	11,546us-gaap_LongTermInvestments	11,856us-gaap_LongTermInvestments
Cash, cash equivalents, and investments	112,642ipi_CashAndCashEquivalentsAndInvestments	89,879ipi_CashAndCashEquivalentsAndInvestments
Cash
Investment [Line Items]
Cash and cash equivalents	24,213us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_CashMember	16,506us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_CashMember
Commercial paper and money market accounts
Investment [Line Items]
Cash and cash equivalents	42,573us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember	51,083us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember
Corporate bonds
Investment [Line Items]
Short-term investments	33,307us-gaap_ShortTermInvestments / us-gaap_InvestmentTypeAxis = us-gaap_CorporateDebtSecuritiesMember	9,432us-gaap_ShortTermInvestments / us-gaap_InvestmentTypeAxis = us-gaap_CorporateDebtSecuritiesMember
Long-term investments	11,546us-gaap_LongTermInvestments / us-gaap_InvestmentTypeAxis = us-gaap_CorporateDebtSecuritiesMember	11,856us-gaap_LongTermInvestments / us-gaap_InvestmentTypeAxis = us-gaap_CorporateDebtSecuritiesMember
Certificates of deposit and time deposits
Investment [Line Items]
Short-term investments	$ 1,003us-gaap_ShortTermInvestments / us-gaap_InvestmentTypeAxis = us-gaap_BankTimeDepositsMember	$ 1,002us-gaap_ShortTermInvestments / us-gaap_InvestmentTypeAxis = us-gaap_BankTimeDepositsMember

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Carrying value of cash and cash equivalents and short-term and long-term investments at the balance sheet date.

+ References

No definition available.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951



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

-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=6507016



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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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



Reference 5: http://www.xbrl.org/2003/role/presentationRef

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

+ References

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

+ References

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-Publisher FASB

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