Supplemental Guarantor Information (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands		Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2014
Assets
Cash and cash equivalents		$ 720,861	$ 593,000	$ 560,341	$ 358,768
Receivables		244,213	231,665
Inventory, Operative Builders		3,263,386	3,403,228
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		64,794	64,016
Deferred tax assets, net		633,637	738,985
Other assets		102,498	91,145
Investments in subsidiaries		0	0
Total assets		5,041,515	5,131,624
Due from Affiliates		0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		789,393	766,327
Notes payable		2,324,845	2,640,149
Financial services		966	2,003
Due to Affiliate		0	0
Stockholder's equity		1,926,311	1,723,145	1,690,834	1,595,910
Total liabilities and Stockholders' equity		5,041,515	5,131,624
KB Home Corporate
Assets
Cash and cash equivalents		575,193	463,100	444,850	303,280
Receivables		24,815	4,807
Inventory, Operative Builders		0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0	0
Deferred tax assets, net		250,747	276,737
Other assets		91,592	79,526
Investments in subsidiaries		49,776	35,965
Total assets		4,406,360	4,419,147
Due from Affiliates		3,414,237	3,559,012
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		163,984	131,530
Notes payable		2,289,532	2,548,112
Financial services		0	0
Due to Affiliate		26,533	16,360
Stockholder's equity		1,926,311	1,723,145
Total liabilities and Stockholders' equity		4,406,360	4,419,147
Guarantor Subsidiaries
Assets
Cash and cash equivalents		102,661	100,439	96,741	36,412
Receivables		144,076	135,915
Inventory, Operative Builders		2,929,466	3,048,132
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		62,290	61,517
Deferred tax assets, net		243,523	318,077
Other assets		8,424	9,177
Investments in subsidiaries		0	0
Total assets		3,490,440	3,673,257
Due from Affiliates		0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		371,909	397,605
Notes payable		9,283	66,927
Financial services		0	0
Due to Affiliate		3,109,248	3,208,725
Stockholder's equity		0	0
Total liabilities and Stockholders' equity		3,490,440	3,673,257
Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents		43,007	29,461	18,750	19,076
Receivables		75,322	90,943
Inventory, Operative Builders		333,920	355,096
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		2,504	2,499
Deferred tax assets, net		139,367	144,171
Other assets		2,482	2,442
Investments in subsidiaries		0	0
Total assets		716,720	731,259
Due from Affiliates		107,992	97,062
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		253,500	237,192
Notes payable		26,030	25,110
Financial services		966	2,003
Due to Affiliate		386,448	430,989
Stockholder's equity		49,776	35,965
Total liabilities and Stockholders' equity		716,720	731,259
Homebuilding [Member]
Assets
Cash and cash equivalents		720,630	592,086	559,042
Total assets		5,029,158	5,121,125
Liabilities and stockholders' equity
Total Homebuilding		3,114,238	3,406,476
Homebuilding [Member] | KB Home Corporate
Assets
Cash and cash equivalents		575,193	463,100
Total assets		942,347	824,170
Liabilities and stockholders' equity
Total Homebuilding		2,453,516	2,679,642
Homebuilding [Member] | Guarantor Subsidiaries
Assets
Cash and cash equivalents		102,661	100,439
Total assets		3,490,440	3,673,257
Liabilities and stockholders' equity
Total Homebuilding		381,192	464,532
Homebuilding [Member] | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents		42,776	28,547
Total assets		596,371	623,698
Liabilities and stockholders' equity
Total Homebuilding		279,530	262,302
Financial services [Member]
Assets
Cash and cash equivalents		231	914	1,299
Receivables		1,724	1,764
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	[1]	10,340	7,771
Other assets		62	50
Total assets		12,357	10,499
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		966	2,003
Financial services [Member] | KB Home Corporate
Assets
Total assets		0	0
Financial services [Member] | Guarantor Subsidiaries
Assets
Total assets		0	0
Financial services [Member] | Non-Guarantor Subsidiaries
Assets
Total assets		12,357	10,499
Consolidating Adjustments
Assets
Cash and cash equivalents		0	0	$ 0	$ 0
Receivables		0	0
Inventory, Operative Builders		0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0	0
Deferred tax assets, net		0	0
Other assets		0	0
Investments in subsidiaries		(49,776)	(35,965)
Total assets		(3,572,005)	(3,692,039)
Due from Affiliates		(3,522,229)	(3,656,074)
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		0	0
Notes payable		0	0
Financial services		0	0
Due to Affiliate		(3,522,229)	(3,656,074)
Stockholder's equity		(49,776)	(35,965)
Total liabilities and Stockholders' equity		(3,572,005)	(3,692,039)
Consolidating Adjustments | Homebuilding [Member]
Assets
Cash and cash equivalents		0	0
Total assets		0	0
Liabilities and stockholders' equity
Total Homebuilding		0	0
Consolidating Adjustments | Financial services [Member]
Assets
Total assets		$ 0	$ 0

[1] In 2017, we made a $5.3 million capital contribution to KBHS and received a $5.0 million distribution from HCM.