Supplemental Guarantor Information (Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018
Assets
Cash and cash equivalents		$ 576,033		$ 454,858	$ 179,764		$ 575,119
Receivables		312,928		249,055
Inventories		3,607,465		3,704,602
Property and equipment, net		65,764		65,043
Other assets		126,588		83,041
Total assets		5,042,002		5,015,482
Liabilities and stockholders’ equity
Mortgages and notes payable		1,766,539		1,748,747
Intercompany payables		0		0
Stockholders’ equity		2,490,354	$ 2,443,104	2,383,122	2,195,210	$ 2,128,497	2,087,500
Total liabilities and stockholders’ equity		5,042,002		5,015,482
Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Cash and cash equivalents		480,206		357,966	94,391		429,977
Total assets		4,418,024		4,298,971
Liabilities and stockholders’ equity
Intercompany payables		73,710		60,964
Stockholders’ equity		2,490,354		2,383,122
Total liabilities and stockholders’ equity		4,418,024		4,298,971
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		65,410		65,434	71,436		114,269
Total assets		3,789,980		3,981,908
Liabilities and stockholders’ equity
Intercompany payables		3,421,590		3,520,090
Stockholders’ equity		0		0
Total liabilities and stockholders’ equity		3,789,980		3,981,908
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		30,417		31,458	13,937		30,873
Total assets		674,091		660,459
Liabilities and stockholders’ equity
Intercompany payables		214,924		229,049
Stockholders’ equity		129,869		115,753
Total liabilities and stockholders’ equity		674,091		660,459
Consolidating Adjustments [Member]
Assets
Cash and cash equivalents		0		0	0		$ 0
Total assets		(3,840,093)		(3,925,856)
Liabilities and stockholders’ equity
Intercompany payables		(3,710,224)		(3,810,103)
Stockholders’ equity		(129,869)		(115,753)
Total liabilities and stockholders’ equity		(3,840,093)		(3,925,856)
Home Building [Member]
Assets
Cash and cash equivalents		575,006		453,814	178,876
Receivables		312,928		249,055
Inventories		3,607,465		3,704,602
Investments in unconsolidated joint ventures		57,823		57,038
Property and equipment, net		65,764		65,043
Deferred tax assets, net		257,571		364,493
Other assets		126,588		83,041
Intercompany receivables		0		0
Investments in subsidiaries		0		0
Total assets		5,003,145		4,977,086
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		783,261		881,555
Mortgages and notes payable		1,766,539		1,748,747
Total Liabilities		2,549,800		2,630,302
Home Building [Member] | Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Cash and cash equivalents		480,206		357,966
Receivables		83,709		1,934
Inventories		0		0
Investments in unconsolidated joint ventures		0		0
Property and equipment, net		27,136		24,250
Deferred tax assets, net		87,382		96,301
Other assets		98,866		78,686
Intercompany receivables		3,510,856		3,624,081
Investments in subsidiaries		129,869		115,753
Total assets		777,299		559,137
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		137,402		139,137
Mortgages and notes payable		1,716,558		1,715,748
Total Liabilities		1,853,960		1,854,885
Home Building [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		65,410		65,434
Receivables		167,965		181,047
Inventories		3,273,411		3,400,307
Investments in unconsolidated joint ventures		57,823		57,038
Property and equipment, net		35,328		37,539
Deferred tax assets, net		169,356		237,877
Other assets		20,687		2,666
Intercompany receivables		0		0
Investments in subsidiaries		0		0
Total assets		3,789,980		3,981,908
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		343,519		453,929
Mortgages and notes payable		24,871		7,889
Total Liabilities		368,390		461,818
Home Building [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		29,390		30,414
Receivables		61,254		66,074
Inventories		334,054		304,295
Investments in unconsolidated joint ventures		0		0
Property and equipment, net		3,300		3,254
Deferred tax assets, net		833		30,315
Other assets		7,035		1,689
Intercompany receivables		199,368		186,022
Investments in subsidiaries		0		0
Total assets		435,866		436,041
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		302,340		288,489
Mortgages and notes payable		25,110		25,110
Total Liabilities		327,450		313,599
Home Building [Member] | Consolidating Adjustments [Member]
Assets
Cash and cash equivalents		0		0
Receivables		0		0
Inventories		0		0
Investments in unconsolidated joint ventures		0		0
Property and equipment, net		0		0
Deferred tax assets, net		0		0
Other assets		0		0
Intercompany receivables		(3,710,224)		(3,810,103)
Investments in subsidiaries		(129,869)		(115,753)
Total assets		0		0
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		0		0
Mortgages and notes payable		0		0
Total Liabilities		0		0
Financial Service [Member]
Assets
Cash and cash equivalents		1,027		1,044	$ 888
Receivables		1,690		2,232
Investments in unconsolidated joint ventures		14,243		14,374
Other assets	[1]	21,897		20,746
Total assets		38,857		38,396
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		1,848		2,058
Financial services		1,848		2,058
Financial Service [Member] | Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Total assets		0		0
Liabilities and stockholders’ equity
Financial services		0		0
Financial Service [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Total assets		0		0
Liabilities and stockholders’ equity
Financial services		0		0
Financial Service [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Total assets		38,857		38,396
Liabilities and stockholders’ equity
Financial services		1,848		2,058
Financial Service [Member] | Consolidating Adjustments [Member]
Assets
Total assets		0		0
Liabilities and stockholders’ equity
Financial services		$ 0		$ 0

[1] Other assets at May 31, 2020 and November 30, 2019 included $21.5 million and $20.6 million, respectively, of contract assets for estimated future renewal commissions related to then-existing insurance policies.