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Revolving Credit Facility (Details) (USD $) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2012 | Feb. 06, 2015
Line of Credit Facility [Line Items] |  |  |
Term of revolving credit facility (in years) | 4 years |  |
Line of credit facility | $ 100,000,000 us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity |  |
Maximum borrowing capacity | 150,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity |  |
Percentage of subsidiary stock securing debt (in hundredths) | 65.00%nsp_PercentageOfSubsidiaryStockSecuringDebt |  |
Unused commitment fee on the average daily unused portion (in hundredths) | 0.25%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage |  |
Letters of Credit Outstanding, Amount | 600,000 us-gaap_LettersOfCreditOutstandingAmount |  |
Special dividend | 50,664,000 nsp_SpecialDividend | 25,700,000 nsp_SpecialDividend |
Alternate base rates, applicable margins [Abstract] |  |  |
Applicable margin, federal funds rate (in hundredths) | 0.50%nsp_ApplicableMarginFederalFundsRate |  |
Applicable margin, 30-day LIBOR (in hundredths) | 2.00%nsp_ApplicableMargin30DayLibor |  |
Subsequent Event [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Line of credit facility |  |  | $ 125,000,000 us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
LIBOR Borrowings [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Description of basis for variable rate | LIBOR |  |
Applicable margin on variable rate on borrowings, minimum (in hundredths) | 2.00%nsp_DebtInstrumentBasisSpreadOnVariableRateMinimum / us-gaap_CreditFacilityAxis = nsp_LiborBorrowingsMember |  |
Applicable margin on variable rate on borrowings, maximum (in hundredths) | 2.75%nsp_DebtInstrumentBasisSpreadOnVariableRateMaximum / us-gaap_CreditFacilityAxis = nsp_LiborBorrowingsMember |  |
Alternate Base Rate Borrowings [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Description of basis for variable rate | alternate base rate |  |
Applicable margin on variable rate on borrowings, minimum (in hundredths) | 0.00%nsp_DebtInstrumentBasisSpreadOnVariableRateMinimum / us-gaap_CreditFacilityAxis = nsp_AlternateBaseRateBorrowingsMember |  |
Applicable margin on variable rate on borrowings, maximum (in hundredths) | 0.75%nsp_DebtInstrumentBasisSpreadOnVariableRateMaximum / us-gaap_CreditFacilityAxis = nsp_AlternateBaseRateBorrowingsMember |  |

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- Details
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- Definition Applicable margin to the LIBOR rate for alternate base rate borrowings. + References No definition available. + Details
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Namespace Prefix: | nsp_
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Balance Type: | na
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- Definition Applicable margin to the federal funds rate for alternate base rate borrowings. + References No definition available. + Details
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- Definition The reference rate for the variable rate of the credit facility, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. + References No definition available. + Details
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- Definition Maximum 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 Minimum 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 Percentage of subsidiary stock securing debt per debt agreements. + References No definition available. + Details
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- Definition Amount of cash outflow in the form of special dividends (not ordinary) to common shareholders of the parent entity. + References No definition available. + Details
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Balance Type: | debit
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- Definition The length of time the borrowing may be outstanding. + References No definition available. + Details
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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- Definition Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
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- Details
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- Details
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- Details
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