v3.25.4
Document and Entity Information - USD ($)
$ in Billions
 12 Months Ended
Dec. 31, 2025
Feb. 03, 2026
Jun. 30, 2025
Cover [Abstract]      
Document Type 10-K    
Document Period End Date Dec. 31, 2025    
Document Transition Report false    
Entity File Number 1-13998    
Entity Registrant Name Insperity, Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 76-0479645    
Entity Address, Address Line One 19001 Crescent Springs Drive    
Entity Address, City or Town Kingwood,    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77339    
City Area Code 281    
Local Phone Number 358-8986    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Common Stock, Shares Outstanding   37,728,423  
Entity Central Index Key 0001000753    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Information [Line Items]      
Entity Registrant Name Insperity, Inc.    
Entity Shell Company false    
Entity Emerging Growth Company false    
Document Annual Report true    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Public Float     $ 2.1
Auditor Name Ernst & Young LLP    
Auditor Location Houston, Texas    
Common Stock [Member]      
Entity Information [Line Items]      
Title of 12(b) Security Common Stock, $0.01 par value per share    
Trading Symbol NSP    
Security Exchange Name NYSE