Supplemental Guarantor Information (Details 2) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended				9 Months Ended
	Dec. 31, 2010	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Aug. 31, 2010	Aug. 31, 2011	Aug. 31, 2010
Cash flows from operating activities:
Net income (loss)		$ (9,649)			$ (1,397)	$ (192,679)	$ (86,810)
Adjustments to reconcile net loss to net cash used by operating activities:
Equity in (income) loss of unconsolidated joint ventures						56,241	(1,267)
Loss on loan guaranty			14,600	22,800		37,330	0
Gain on sale of operating property	(8,800)					(8,825)	0
Inventory impairments and land option contract abandonments						23,507	16,739
Change in assets and liabilities:
Receivables						(10,940)	182,762
Inventories						(177,770)	(149,021)
Accounts payable, accrued expenses and other liabilities						(46,953)	(147,323)
Other, net						10,150	20,777
Net cash used by operating activities						(309,939)	(164,143)
Cash flows from investing activities:
Investments in unconsolidated joint ventures						(1,974)	(1,533)
Proceeds from sale of operating property	80,600					80,600	0
Purchases of property and equipment, net						(74)	(642)
Net cash provided (used) by investing activities						78,552	(2,175)
Cash flows from financing activities:
Change in restricted cash						2,291	(2,092)
Repayment of senior notes						(100,000)	0
Payments on mortgages and land contracts due to land sellers and other loans						(86,064)	(73,371)
Issuance of common stock under employee stock plans						1,426	1,609
Excess tax benefit associated with exercise of stock options						0	583
Payments of cash dividends						(14,423)	(14,415)
Repurchases of common stock						0	(350)
Net cash used by financing activities						(196,770)	(88,036)
Net decrease in cash and cash equivalents						(428,157)	(254,354)
Cash and cash equivalents at beginning of period	908,430			908,430		908,430	1,177,961
Cash and cash equivalents at end of period		480,273			923,607	480,273	923,607
Supplemental Guarantor Information (Textuals) [Abstract]
Ownership share in guarantor subsidiaries						100.00%
KB Home Corporate[Member]
Cash flows from operating activities:
Net income (loss)		(9,649)			(1,397)	(192,679)	(86,610)
Change in assets and liabilities:
Receivables						77,094	182,187
Accounts payable, accrued expenses and other liabilities						(3,127)	(27,757)
Other, net						6,566	(7,304)
Net cash used by operating activities						(112,146)	60,516
Cash flows from investing activities:
Purchases of property and equipment, net						(178)	(213)
Net cash provided (used) by investing activities						(178)	(213)
Cash flows from financing activities:
Change in restricted cash						23,692	22,689
Repayment of senior notes						(100,000)	0
Issuance of common stock under employee stock plans						1,426	1,609
Excess tax benefit associated with exercise of stock options						0	583
Payments of cash dividends						(14,423)	(14,415)
Repurchases of common stock						0	(350)
Intercompany						(146,568)	(288,924)
Net cash used by financing activities						(235,873)	(278,808)
Net decrease in cash and cash equivalents						(348,197)	(218,505)
Cash and cash equivalents at beginning of period	770,603			770,603		770,603	995,122
Cash and cash equivalents at end of period		422,406			776,617	422,406	776,617
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net income (loss)		(10,360)			(1,445)	(23,989)	(25,443)
Adjustments to reconcile net loss to net cash used by operating activities:
Equity in (income) loss of unconsolidated joint ventures						5	148
Gain on sale of operating property						(8,825)	0
Inventory impairments and land option contract abandonments						991	1,671
Change in assets and liabilities:
Receivables						(4,247)	(3,027)
Inventories						(49,142)	(60,018)
Accounts payable, accrued expenses and other liabilities						(19,985)	(29,692)
Other, net						(2,989)	867
Net cash used by operating activities						(108,181)	(115,494)
Cash flows from investing activities:
Investments in unconsolidated joint ventures						(1,344)	(212)
Proceeds from sale of operating property						80,600	0
Purchases of property and equipment, net						(81)	(63)
Net cash provided (used) by investing activities						79,185	(275)
Cash flows from financing activities:
Change in restricted cash							(24,781)
Payments on mortgages and land contracts due to land sellers and other loans						(84,638)	(53,354)
Intercompany						123,481	154,796
Net cash used by financing activities						38,843	76,661
Net decrease in cash and cash equivalents						9,847	(39,108)
Cash and cash equivalents at beginning of period	3,619			3,619		3,619	44,478
Cash and cash equivalents at end of period		13,466			5,370	13,466	5,370
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net income (loss)		(7,110)			1,156	(166,985)	(16,978)
Adjustments to reconcile net loss to net cash used by operating activities:
Equity in (income) loss of unconsolidated joint ventures						56,236	(1,415)
Loss on loan guaranty						37,330
Inventory impairments and land option contract abandonments						22,516	15,068
Change in assets and liabilities:
Receivables						(83,787)	3,602
Inventories						(128,628)	(89,003)
Accounts payable, accrued expenses and other liabilities						(23,841)	(89,874)
Other, net						6,573	27,214
Net cash used by operating activities						(280,586)	(151,386)
Cash flows from investing activities:
Investments in unconsolidated joint ventures						(640)	(1,321)
Purchases of property and equipment, net						185	(366)
Net cash provided (used) by investing activities						(455)	(1,687)
Cash flows from financing activities:
Change in restricted cash						(21,401)	0
Payments on mortgages and land contracts due to land sellers and other loans						(1,426)	(20,017)
Intercompany						214,061	176,349
Net cash used by financing activities						191,234	156,332
Net decrease in cash and cash equivalents						(89,807)	3,259
Cash and cash equivalents at beginning of period	134,208			134,208		134,208	138,361
Cash and cash equivalents at end of period		44,401			141,620	44,401	141,620
Consolidating Adjustments [Member]
Cash flows from operating activities:
Net income (loss)		17,470			289	190,974	42,221
Change in assets and liabilities:
Net cash used by operating activities						190,974	42,221
Cash flows from financing activities:
Intercompany						(190,974)	(42,221)
Net cash used by financing activities						(190,974)	(42,221)
Cash and cash equivalents at beginning of period	0			0		0	0
Cash and cash equivalents at end of period		$ 0			$ 0	$ 0	$ 0