Basis of Presentation (Details)	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Percentage of PEO revenues from the Company's Texas markets (in hundredths)	25.00%	26.00%
Percentage of PEO revenues from the Company's California markets (in hundredths)	18.00%	17.00%

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