Supplemental Guarantor Information (Condensed Consolidating Statements of Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2017
Net income	$ 123,167	$ 68,136	$ 47,461	$ 30,011	$ 96,836	$ 87,476	$ 57,308	$ (71,255)	$ 268,775	$ 170,365	$ 180,595
Other Comprehensive Income (Loss), before Reclassifications, before Tax									(8,138)	10,108	(1,445)
Other Comprehensive Income (Loss), before Tax									(8,138)	10,108	(1,445)
Income tax benefit (expense) related to items of other comprehensive income (loss)									2,197	(2,749)	578
Other comprehensive income (loss), net of tax									(5,941)	7,359	(867)
Comprehensive income									262,834	177,724	179,728
Reportable Legal Entities [Member] | KB Home Corporate
Net income									157,869	170,365	180,595
Other Comprehensive Income (Loss), before Reclassifications, before Tax									(8,138)	10,108	(1,445)
Other Comprehensive Income (Loss), before Tax									(8,138)	10,108	(1,445)
Income tax benefit (expense) related to items of other comprehensive income (loss)									2,197	(2,749)	578
Other comprehensive income (loss), net of tax									(5,941)	7,359	(867)
Comprehensive income									151,928	177,724	179,728
Reportable Legal Entities [Member] | Guarantor Subsidiaries
Net income									190,180	207,467	171,770
Other Comprehensive Income (Loss), before Reclassifications, before Tax									0	0	0
Other Comprehensive Income (Loss), before Tax									0	0	0
Income tax benefit (expense) related to items of other comprehensive income (loss)									0	0	0
Other comprehensive income (loss), net of tax									0	0	0
Comprehensive income									190,180	207,467	171,770
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries
Net income									9,365	(37,564)	12,831
Other Comprehensive Income (Loss), before Reclassifications, before Tax									0	0	0
Other Comprehensive Income (Loss), before Tax									0	0	0
Income tax benefit (expense) related to items of other comprehensive income (loss)									0	0	0
Other comprehensive income (loss), net of tax									0	0	0
Comprehensive income									9,365	(37,564)	12,831
Consolidating Adjustments
Net income									(88,639)	(169,903)	(184,601)
Other Comprehensive Income (Loss), before Reclassifications, before Tax									0	0	0
Other Comprehensive Income (Loss), before Tax									0	0	0
Income tax benefit (expense) related to items of other comprehensive income (loss)									0	0	0
Other comprehensive income (loss), net of tax									0	0	0
Comprehensive income									$ (88,639)	$ (169,903)	$ (184,601)