Cover - USD ($)	12 Months Ended
	Nov. 30, 2020	Dec. 31, 2020	May 31, 2020	Nov. 30, 2019
Document Information [Line Items]
Document Type	10-K
Document Quarterly Report	true
Document Period End Date	Nov. 30, 2020
Document Transition Report	false
Entity File Number	001-09195
Entity Registrant Name	KB HOME
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	95-3666267
Entity Address, Address Line One	10990 Wilshire Boulevard
Entity Address, City or Town	Los Angeles
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90024
City Area Code	310
Local Phone Number	231-4000
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 3,236,693,083
Grantor stock ownership trust	7,124,317		7,317,336	7,630,582
Treasury Stock, Common, Shares			24,525,786
Entity Common Stock Shares Outstanding		91,637,771
Documents Incorporated by Reference [Text Block]	Portions of the registrant’s definitive Proxy Statement for the 2021 Annual Meeting of Stockholders (incorporated into Part III).
Entity Central Index Key	0000795266
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--11-30
Subsequent Event
Document Information [Line Items]
Grantor stock ownership trust		7,124,317
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock (par value $1.00 per share)
Trading Symbol	KBH
Security Exchange Name	NYSE
Rights
Document Information [Line Items]
Title of 12(b) Security	Rights to Purchase Series A Participating Cumulative Preferred Stock
Trading Symbol	KBH
Security Exchange Name	NYSE