Document and Entity Information - USD ($)	12 Months Ended
	Jun. 30, 2019	Jul. 31, 2019	Dec. 31, 2018
Document and Entity Information
Entity Registrant Name	K12 INC
Entity Central Index Key	0001157408
Document Type	10-K
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Current Fiscal Year End Date	--06-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 704,767,553
Entity Common Stock, Shares Outstanding		40,245,366
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false