Commitments and Contingencies (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2003
Commitments and Contingencies [Abstract]
Unemployment tax reserve account assessment relating to California employees, including penalties and interest	$ 8.1	$ 5.6

Name:

nsp_UnemploymentTaxReserveAccountAssessmentRelatingToCaliforniaEmployeesIncludingPenaltiesAndInterest

Namespace Prefix:

nsp

Data Type:

xbrli:monetaryItemType

Balance Type:

debit

Period Type:

instant