Supplemental Guarantor Information (Condensed Consolidating Statements of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2010
Condensed Consolidated Statements of Operations
Revenues	$ 578,201	$ 424,504	$ 302,852	$ 254,558	$ 479,872	$ 367,316	$ 271,738	$ 196,940	$ 1,560,115	$ 1,315,866	$ 1,589,996
Homebuilding:
Revenues									1,548,432	1,305,562	1,581,763
Construction and land costs									(1,317,529)	(1,129,985)	(1,308,288)
Selling, general and administrative expenses									(251,159)	(247,886)	(289,520)
Loss on loan guaranty							(14,600)	(22,800)	0	(30,765)	0
Operating income (loss)									(20,256)	(103,074)	(16,045)
Interest income									518	871	2,098
Interest expense									(69,804)	(49,204)	(68,307)
Equity in income (loss) of unconsolidated joint ventures									(394)	(55,839)	(6,257)
Homebuilding pretax loss									(89,936)	(207,246)	(88,511)
Financial services pretax income									10,883	26,078	12,143
Total pretax loss	2,424	(7,439)	(28,636)	(45,402)	11,411	(9,649)	(68,804)	(114,126)	(79,053)	(181,168)	(76,368)
Income tax benefit									20,100	2,400	7,000
Equity in net loss of subsidiaries									0	0	0
Net loss	7,724	3,261	(24,136)	(45,802)	13,911	(9,649)	(68,504)	(114,526)	(58,953)	(178,768)	(69,368)
KB Home Corporate
Condensed Consolidated Statements of Operations
Revenues									0	0	0
Homebuilding:
Revenues									0	0	0
Construction and land costs									0	0	0
Selling, general and administrative expenses									(60,101)	(52,784)	(68,149)
Loss on loan guaranty										0
Operating income (loss)									(60,101)	(52,784)	(68,149)
Interest income									480	715	1,770
Interest expense									49,686	51,957	20,353
Equity in income (loss) of unconsolidated joint ventures									0	0	0
Homebuilding pretax loss									(9,935)	(112)	(46,026)
Financial services pretax income									0	0	0
Total pretax loss									(9,935)	(112)	(46,026)
Income tax benefit									2,500	0	4,200
Equity in net loss of subsidiaries									(51,518)	(178,656)	(27,542)
Net loss									(58,953)	(178,768)	(69,368)
Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues									978,064	745,965	429,917
Homebuilding:
Revenues									978,064	745,965	429,917
Construction and land costs									(844,982)	(638,802)	(360,450)
Selling, general and administrative expenses									(119,431)	(93,288)	(48,233)
Loss on loan guaranty										(30,765)
Operating income (loss)									13,651	(16,890)	21,234
Interest income									0	36	30
Interest expense									(78,879)	(69,309)	(41,686)
Equity in income (loss) of unconsolidated joint ventures									(983)	(55,831)	(186)
Homebuilding pretax loss									(66,211)	(141,994)	(20,608)
Financial services pretax income									0	0	0
Total pretax loss									(66,211)	(141,994)	(20,608)
Income tax benefit									16,900	1,900	1,900
Equity in net loss of subsidiaries									0	0	0
Net loss									(49,311)	(140,094)	(18,708)
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues									582,051	569,901	1,160,079
Homebuilding:
Revenues									570,368	559,597	1,151,846
Construction and land costs									(472,547)	(491,183)	(947,838)
Selling, general and administrative expenses									(71,627)	(101,814)	(173,138)
Loss on loan guaranty										0
Operating income (loss)									26,194	(33,400)	30,870
Interest income									38	120	298
Interest expense									(40,611)	(31,852)	(46,974)
Equity in income (loss) of unconsolidated joint ventures									589	(8)	(6,071)
Homebuilding pretax loss									(13,790)	(65,140)	(21,877)
Financial services pretax income									10,883	26,078	12,143
Total pretax loss									(2,907)	(39,062)	(9,734)
Income tax benefit									700	500	900
Equity in net loss of subsidiaries									0	0	0
Net loss									(2,207)	(38,562)	(8,834)
Consolidating Adjustments
Condensed Consolidated Statements of Operations
Revenues									0	0	0
Homebuilding:
Revenues									0	0	0
Construction and land costs									0	0	0
Selling, general and administrative expenses									0	0	0
Loss on loan guaranty										0
Operating income (loss)									0	0	0
Interest income									0	0	0
Interest expense									0	0	0
Equity in income (loss) of unconsolidated joint ventures									0	0	0
Homebuilding pretax loss									0	0	0
Financial services pretax income									0	0	0
Total pretax loss									0	0	0
Income tax benefit									0	0	0
Equity in net loss of subsidiaries									51,518	178,656	27,542
Net loss									$ 51,518	$ 178,656	$ 27,542