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Applicable margin to the LIBOR rate for alternate base rate borrowings.

+ References

No definition available.

+ Details

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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

Name:	nsp_DebtInstrumentBasisSpreadOnVariableRateMinimum
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- Definition

Percentage of subsidiary stock securing debt per debt agreements.

+ References

No definition available.

+ Details

Name:	nsp_PercentageOfSubsidiaryStockSecuringDebt
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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
Period Type:	duration

- 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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Balance Type:	credit
Period Type:	instant

- 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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Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LineOfCreditFacilityLineItems
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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

+ Details

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Balance Type:	credit
Period Type:	instant

- 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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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

Name:	us-gaap_CreditFacilityAxis=nsp_LiborBorrowingsMember
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- Details

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Revolving Credit Facility (Details) (USD $)	12 Months Ended
Revolving Credit Facility (Details) (USD $)	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
Maximum borrowing capacity	150,000,000
Percentage of subsidiary stock securing debt (in hundredths)	65.00%
Unused commitment fee on the average daily unused portion (in hundredths)	0.25%
Letters of Credit Outstanding, Amount	600,000
Special dividend	50,664,000nsp_SpecialDividend	25,700,000nsp_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
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%
Applicable margin on variable rate on borrowings, maximum (in hundredths)	2.75%
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%
Applicable margin on variable rate on borrowings, maximum (in hundredths)	0.75%