Supplemental Guarantor Information (Condensed Consolidating Statements of Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2016
Net income	$ 96,836	$ 87,476	$ 57,308	$ (71,255)	$ 84,346	$ 50,208	$ 31,782	$ 14,259	$ 170,365	$ 180,595	$ 105,615
Other Comprehensive Income (Loss), before Reclassifications, before Tax									10,108	(1,445)	2,103
Other Comprehensive Income (Loss), before Tax									10,108	(1,445)	2,103
Income tax benefit (expense) related to items of other comprehensive income (loss)									(2,749)	578	(841)
Other comprehensive income (loss), net of tax									7,359	(867)	1,262
Comprehensive income									177,724	179,728	106,877
KB Home Corporate
Net income									170,365	180,595	105,615
Other Comprehensive Income (Loss), before Reclassifications, before Tax									10,108	(1,445)	2,103
Other Comprehensive Income (Loss), before Tax									10,108	(1,445)	2,103
Income tax benefit (expense) related to items of other comprehensive income (loss)									(2,749)	578	(841)
Other comprehensive income (loss), net of tax									7,359	(867)	1,262
Comprehensive income									177,724	179,728	106,877
Guarantor Subsidiaries
Net income									207,467	171,770	118,667
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									207,467	171,770	118,667
Non-Guarantor Subsidiaries
Net income									(37,564)	12,831	(62,966)
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									(37,564)	12,831	(62,966)
Consolidating Adjustments
Net income									(169,903)	(184,601)	(55,701)
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									$ (169,903)	$ (184,601)	$ (55,701)