Basis of Presentation (Details)	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011
Basis of Presentation [Abstract]
Percentage of PEO revenues from the Company's Texas markets (in hundredths)	26.00%	27.00%
Percentage of PEO revenues from the Company's California markets (in hundredths)	17.00%	16.00%

A presentation of the revenue percentage from the state of California.

No definition available.

Name:	nsp_PercentageOfRevenuesFromCompanyCaliforniaMarkets
Namespace Prefix:	nsp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration