Document and Entity Information (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	INSPERITY, INC.
Entity Central Index Key	0001000753
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float	$ 619
Entity Common Stock, Shares Outstanding	25,679,598
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2012