CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 228,588	$ 276,456
Restricted cash	45,152	44,040
Marketable securities	28,840us-gaap_MarketableSecuritiesCurrent	28,631us-gaap_MarketableSecuritiesCurrent
Accounts receivable, net:
Trade	3,740us-gaap_AccountsReceivableNetCurrent	12,010us-gaap_AccountsReceivableNetCurrent
Unbilled	252,931nsp_Unbilled	160,154nsp_Unbilled
Other	3,107us-gaap_OtherReceivables	2,952us-gaap_OtherReceivables
Prepaid insurance	36,660us-gaap_PrepaidInsurance	21,301us-gaap_PrepaidInsurance
Assets held for sale	13,495	0
Other current assets	21,080us-gaap_OtherAssetsCurrent	17,649us-gaap_OtherAssetsCurrent
Deferred income taxes	0us-gaap_DeferredTaxAssetsNetCurrent	6,316us-gaap_DeferredTaxAssetsNetCurrent
Total current assets	633,593us-gaap_AssetsCurrent	569,509us-gaap_AssetsCurrent
Property and equipment:
Land	5,214us-gaap_Land	5,214us-gaap_Land
Buildings and improvements	71,008us-gaap_BuildingsAndImprovementsGross	70,471us-gaap_BuildingsAndImprovementsGross
Computer hardware and software	89,367nsp_ComputerHardwareAndSoftware	89,204nsp_ComputerHardwareAndSoftware
Software development costs	41,987nsp_SoftwareDevelopmentCosts	41,314nsp_SoftwareDevelopmentCosts
Furniture, fixtures and other	38,641us-gaap_FurnitureAndFixturesGross	38,617us-gaap_FurnitureAndFixturesGross
Aircraft	0us-gaap_FlightEquipmentOwnedGross	35,866us-gaap_FlightEquipmentOwnedGross
Total property and equipment, gross	246,217us-gaap_PropertyPlantAndEquipmentGross	280,686us-gaap_PropertyPlantAndEquipmentGross
Accumulated depreciation and amortization	(187,102)	(196,341)
Total property and equipment, net	59,115us-gaap_PropertyPlantAndEquipmentNet	84,345us-gaap_PropertyPlantAndEquipmentNet
Other assets:
Prepaid health insurance	9,000nsp_PrepaidHealthInsuranceNoncurrent	9,000nsp_PrepaidHealthInsuranceNoncurrent
Deposits – health insurance	3,700nsp_DepositsHealthInsurance	3,700nsp_DepositsHealthInsurance
Deposits – workers’ compensation	115,640nsp_DepositsWorkersCompensation	113,934nsp_DepositsWorkersCompensation
Goodwill and other intangible assets, net	14,232nsp_GoodwillAndOtherIntangibleAssetsNet	14,457nsp_GoodwillAndOtherIntangibleAssetsNet
Deferred income taxes	3,588	0
Other assets	1,753us-gaap_OtherAssetsNoncurrent	1,725us-gaap_OtherAssetsNoncurrent
Total other assets	147,913us-gaap_OtherAssets	142,816us-gaap_OtherAssets
Total assets	840,621us-gaap_Assets	796,670us-gaap_Assets
Current liabilities:
Accounts payable	3,061us-gaap_AccountsPayableCurrent	4,674us-gaap_AccountsPayableCurrent
Payroll taxes and other payroll deductions payable	176,667	176,341
Accrued worksite employee payroll cost	223,564nsp_AccruedWorksiteEmployeePayrollCosts	192,396nsp_AccruedWorksiteEmployeePayrollCosts
Accrued health insurance costs	25,589nsp_AccruedHealthInsuranceCosts	18,329nsp_AccruedHealthInsuranceCosts
Accrued workers’ compensation costs	47,225	45,592
Accrued corporate payroll and commissions	23,068	32,644
Other accrued liabilities	25,347us-gaap_AccruedLiabilitiesCurrent	22,444us-gaap_AccruedLiabilitiesCurrent
Deferred income taxes	6,944	0
Income taxes payable	280us-gaap_TaxesPayableCurrent	4,031us-gaap_TaxesPayableCurrent
Total current liabilities	531,745us-gaap_LiabilitiesCurrent	496,451us-gaap_LiabilitiesCurrent
Noncurrent liabilities:
Accrued workers’ compensation costs	95,775	92,048
Deferred income taxes	0	4,075
Total noncurrent liabilities	95,775us-gaap_LiabilitiesNoncurrent	96,123us-gaap_LiabilitiesNoncurrent
Commitments and contingencies
Stockholders’ equity:
Common stock	308us-gaap_CommonStockValue	308us-gaap_CommonStockValue
Additional paid-in capital	140,963	137,769
Treasury stock, at cost	(151,599)us-gaap_TreasuryStockValue	(148,465)us-gaap_TreasuryStockValue
Accumulated other comprehensive income, net of tax	5	3
Retained earnings	223,424	214,481
Total stockholders’ equity	213,101us-gaap_StockholdersEquity	204,096us-gaap_StockholdersEquity
Total liabilities and stockholders’ equity	$ 840,621	$ 796,670

Carrying value as of the balance sheet date of the obligations incurred through that date and payable for corporate employees' services provided and commissions. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

No definition available.