Supplemental Guarantor Information (Condensed Consolidating Statements of Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2015
Net income	$ 84,346	$ 50,208	$ 31,782	$ 14,259	$ 37,528	$ 39,363	$ 15,597	$ 13,127	$ 180,595	$ 105,615	$ 84,643
Other Comprehensive Income (Loss), before Reclassifications, before Tax									(1,445)	2,103	6,149
Other Comprehensive Income (Loss), before Tax									(1,445)	2,103	6,149
Income tax benefit (expense) related to items of other comprehensive income (loss)									578	(841)	(2,460)
Other comprehensive income (loss), net of tax									(867)	1,262	3,689
Comprehensive income									179,728	106,877	88,332
KB Home Corporate
Net income									180,595	105,615	84,643
Other Comprehensive Income (Loss), before Reclassifications, before Tax									(1,445)	2,103	6,149
Other Comprehensive Income (Loss), before Tax									(1,445)	2,103	6,149
Income tax benefit (expense) related to items of other comprehensive income (loss)									578	(841)	(2,460)
Other comprehensive income (loss), net of tax									(867)	1,262	3,689
Comprehensive income									179,728	106,877	88,332
Guarantor Subsidiaries
Net income									156,183	90,103	74,937
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									156,183	90,103	74,937
Non-Guarantor Subsidiaries
Net income									28,418	(34,402)	(15,718)
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									28,418	(34,402)	(15,718)
Consolidating Adjustments
Net income									(184,601)	(55,701)	(59,219)
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									$ (184,601)	$ (55,701)	$ (59,219)