Supplemental Guarantor Information (Details) (USD $) In Thousands	3 Months Ended				9 Months Ended
	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Aug. 31, 2010	Aug. 31, 2011	Aug. 31, 2010
Condensed Consolidated Statements of Operations
Total revenues	$ 367,316			$ 501,003	$ 835,994	$ 1,139,033
Homebuilding:
Revenues	364,532			498,821	829,816	1,133,846
Construction and land costs	(302,908)			(411,813)	(724,085)	(945,196)
Selling, general and administrative expenses	(60,185)			(78,602)	(172,310)	(233,795)
Loss on loan guaranty		(14,600)	(22,800)		(37,330)	0
Operating income (loss)	1,439			8,406	(103,909)	(45,145)
Interest income	123			603	776	1,628
Interest Expense	(12,342)			(16,183)	(36,902)	(52,108)
Equity in income (loss) of unconsolidated joint ventures	64			(1,947)	(55,865)	(4,679)
Homebuilding pretax income (loss)	(10,716)			(9,121)	(195,900)	(100,304)
Financial services pretax income	1,067			2,424	3,321	8,494
Total pretax income (loss)	(9,649)			(6,697)	(192,579)	(91,810)
Income tax benefit (expense)	0			5,300	(100)	5,000
Net income (loss)	(9,649)			(1,397)	(192,679)	(86,810)
KB Home Corporate[Member]
Homebuilding:
Selling, general and administrative expenses	(5,522)			(12,767)	(39,361)	(59,796)
Operating income (loss)	(5,522)			(12,767)	(39,361)	(59,796)
Interest income	97			512	631	1,377
Interest Expense	13,246			7,247	37,025	11,430
Homebuilding pretax income (loss)	7,821			(5,008)	(1,705)	(46,989)
Total pretax income (loss)	7,821			(5,008)	(1,705)	(46,989)
Income tax benefit (expense)				3,900		2,600
Equity in net loss of subsidiaries	(17,470)			(289)	(190,974)	(42,221)
Net income (loss)	(9,649)			(1,397)	(192,679)	(86,610)
Guarantor Subsidiaries [Member]
Condensed Consolidated Statements of Operations
Total revenues	109,808			124,534	241,702	307,427
Homebuilding:
Revenues	109,808			124,534	241,702	307,427
Construction and land costs	(92,245)			(106,649)	(206,373)	(263,301)
Selling, general and administrative expenses	(13,800)			(13,731)	(23,735)	(41,940)
Operating income (loss)	3,763			4,154	11,594	2,186
Interest income				15	4	21
Interest Expense	(14,190)			(11,045)	(35,582)	(29,002)
Equity in income (loss) of unconsolidated joint ventures	67			(69)	(5)	(148)
Homebuilding pretax income (loss)	(10,360)			(6,945)	(23,989)	(26,943)
Total pretax income (loss)	(10,360)			(6,945)	(23,989)	(26,943)
Income tax benefit (expense)				5,500		1,500
Net income (loss)	(10,360)			(1,445)	(23,989)	(25,443)
Non-Guarantor Subsidiaries [Member]
Condensed Consolidated Statements of Operations
Total revenues	257,508			376,469	594,292	831,606
Homebuilding:
Revenues	254,724			374,287	588,114	826,419
Construction and land costs	(210,663)			(305,164)	(517,712)	(681,895)
Selling, general and administrative expenses	(40,863)			(52,104)	(109,214)	(132,059)
Loss on loan guaranty					(37,330)
Operating income (loss)	3,198			17,019	(76,142)	12,465
Interest income	26			76	141	230
Interest Expense	(11,398)			(12,385)	(38,345)	(34,536)
Equity in income (loss) of unconsolidated joint ventures	(3)			(1,878)	(55,860)	(4,531)
Homebuilding pretax income (loss)	(8,177)			2,832	(170,206)	(26,372)
Financial services pretax income	1,067			2,424	3,321	8,494
Total pretax income (loss)	(7,110)			5,256	(166,885)	(17,878)
Income tax benefit (expense)				(4,100)	(100)	900
Net income (loss)	(7,110)			1,156	(166,985)	(16,978)
Consolidating Adjustments [Member]
Homebuilding:
Equity in net loss of subsidiaries	17,470			289	190,974	42,221
Net income (loss)	$ 17,470			$ 289	$ 190,974	$ 42,221