The additional number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

Name:	nsp_IncreaseInAuthorizedNumberOfSharesToBeRepurchasedInShares
Namespace Prefix:	nsp
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Equity impact of aggregate cash, stock, and paid-in-kind dividends declared for common shareholders during the period.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 405

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

+ Details

Name:	us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation
Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StockholdersEquityNoteAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 1

-Section B

-Paragraph 11A

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ Details

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Stockholders' Equity (Details) (USD $) In Thousands, except Share data	3 Months Ended						9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Sep. 30, 2011	Sep. 30, 2010
Stockholders' Equity [Abstract]
Authorized number of shares to be repurchased (in shares)							1,000,000
Shares were repurchased under the program (in shares)							787,304
Shares withheld for tax withholding obligations for the vesting of restricted stock awards (in shares)							108,280
Authorized to repurchased additional Shares under repurchase program (in shares)	1,352,089						1,352,089
Dividends declared per share of common stock (in dollars per share)	$ 0.15	$ 0.15	$ 0.15	$ 0.13	$ 0.13	$ 0.13
Dividend paid							$ 11,871	$ 10,100