Supplemental Guarantor Information (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands		Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2015
Assets
Cash and cash equivalents		$ 575,119	$ 720,861	$ 593,000	$ 560,341
Receivables		292,830	244,213
Inventory, Operative Builders		3,582,839	3,263,386
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		61,960	64,794
Deferred tax assets, net		441,820	633,637
Other assets		107,383	102,498
Investments in subsidiaries		0	0
Total assets		5,073,571	5,041,515
Due from Affiliates		0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		924,313	789,393
Notes payable		2,060,263	2,324,845
Financial services		1,495	966
Due to Affiliate		0	0
Stockholder's equity		2,087,500	1,926,311	1,723,145	1,690,834
Total liabilities and Stockholders' equity		5,073,571	5,041,515
KB Home Corporate
Assets
Cash and cash equivalents		429,977	575,193	463,100	444,850
Receivables		5,135	24,815
Inventory, Operative Builders		0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0	0
Deferred tax assets, net		84,564	250,747
Other assets		95,738	91,592
Investments in subsidiaries		67,657	49,776
Total assets		4,252,493	4,406,360
Due from Affiliates		3,569,422	3,414,237
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		126,176	163,984
Notes payable		1,995,115	2,289,532
Financial services		0	0
Due to Affiliate		43,702	26,533
Stockholder's equity		2,087,500	1,926,311
Total liabilities and Stockholders' equity		4,252,493	4,406,360
Guarantor Subsidiaries
Assets
Cash and cash equivalents		114,269	104,120	105,903	99,445
Receivables		198,465	145,067
Inventory, Operative Builders		3,314,386	2,959,606
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		61,960	64,794
Deferred tax assets, net		303,669	243,523
Other assets		9,530	8,954
Investments in subsidiaries		0	0
Total assets		4,002,279	3,526,064
Due from Affiliates		0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		584,321	374,051
Notes payable		40,038	9,283
Financial services		0	0
Due to Affiliate		3,377,920	3,142,730
Stockholder's equity		0	0
Total liabilities and Stockholders' equity		4,002,279	3,526,064
Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents		30,873	41,548	23,997	16,046
Receivables		89,230	74,331
Inventory, Operative Builders		268,453	303,780
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0	0
Deferred tax assets, net		53,587	139,367
Other assets		2,115	1,952
Investments in subsidiaries		0	0
Total assets		614,638	681,096
Due from Affiliates		158,760	107,992
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		213,816	251,358
Notes payable		25,110	26,030
Financial services		1,495	966
Due to Affiliate		306,560	352,966
Stockholder's equity		67,657	49,776
Total liabilities and Stockholders' equity		614,638	681,096
Homebuilding [Member]
Assets
Cash and cash equivalents		574,359	720,630	592,086
Total assets		5,061,191	5,029,158
Liabilities and stockholders' equity
Total Homebuilding		2,984,576	3,114,238
Homebuilding [Member] | KB Home Corporate
Assets
Cash and cash equivalents		429,977	575,193
Total assets		615,414	942,347
Liabilities and stockholders' equity
Total Homebuilding		2,121,291	2,453,516
Homebuilding [Member] | Guarantor Subsidiaries
Assets
Cash and cash equivalents		114,269	104,120
Total assets		4,002,279	3,526,064
Liabilities and stockholders' equity
Total Homebuilding		624,359	383,334
Homebuilding [Member] | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents		30,113	41,317
Total assets		443,498	560,747
Liabilities and stockholders' equity
Total Homebuilding		238,926	277,388
Financial services [Member]
Assets
Cash and cash equivalents		760	231	914
Receivables		2,885	1,724
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	[1]	8,594	10,340
Other assets		141	62
Total assets		12,380	12,357
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		1,495	966
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		12,380	12,357
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		(67,657)	(49,776)
Total assets		(3,795,839)	(3,572,005)
Due from Affiliates		(3,728,182)	(3,522,229)
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		0	0
Notes payable		0	0
Financial services		0	0
Due to Affiliate		(3,728,182)	(3,522,229)
Stockholder's equity		(67,657)	(49,776)
Total liabilities and Stockholders' equity		(3,795,839)	(3,572,005)
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.