Supplemental Guarantor Information (Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		May 31, 2019	Feb. 28, 2019	Dec. 01, 2018	Nov. 30, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017
Assets
Cash and cash equivalents		$ 179,764			$ 575,119	$ 670,554		$ 720,861
Receivables		299,708			292,830
Inventories		3,780,853			3,582,839
Investments in unconsolidated joint ventures		56,446			61,960
Property and equipment, net		61,221			24,283
Other assets		87,734			83,100
Total assets		4,919,953			5,073,571
Liabilities and stockholders’ equity
Mortgages and notes payable		1,854,556			2,060,263
Intercompany payables		0			0
Stockholders’ equity		2,195,210	$ 2,128,497		2,087,500	1,914,643	$ 1,852,722	1,926,311
Total liabilities and stockholders’ equity		4,919,953			5,073,571
Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Cash and cash equivalents		94,391			429,977	542,126		575,193
Total assets		4,178,912			4,252,493
Liabilities and stockholders’ equity
Intercompany payables		52,112			43,702
Stockholders’ equity		2,195,210			2,087,500
Total liabilities and stockholders’ equity		4,178,912			4,252,493
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		71,436			114,269	95,431		104,120
Total assets		4,185,726			4,002,279
Liabilities and stockholders’ equity
Intercompany payables		3,688,956			3,377,920
Stockholders’ equity		0			0
Total liabilities and stockholders’ equity		4,185,726			4,002,279
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		13,937			30,873	32,997		41,548
Total assets		631,063			614,638
Liabilities and stockholders’ equity
Intercompany payables		238,904			306,560
Stockholders’ equity		95,776			67,657
Total liabilities and stockholders’ equity		631,063			614,638
Consolidating Adjustments [Member]
Assets
Cash and cash equivalents		0			0	0		$ 0
Total assets		(4,075,748)			(3,795,839)
Liabilities and stockholders’ equity
Intercompany payables		(3,979,972)			(3,728,182)
Stockholders’ equity		(95,776)			(67,657)
Total liabilities and stockholders’ equity		(4,075,748)			(3,795,839)
Home Building [Member]
Assets
Cash and cash equivalents		178,876			574,359	669,798
Receivables		299,708			292,830
Inventories		3,780,853		$ 3,547,551	3,582,839
Investments in unconsolidated joint ventures		56,446			61,960
Property and equipment, net		61,221		55,477	24,283
Deferred tax assets, net		424,395		437,796	441,820
Other assets		87,734			83,100
Intercompany receivables		0			0
Investments in subsidiaries		0			0
Total assets		4,889,233			5,061,191
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		868,736			924,313
Mortgages and notes payable		1,854,556			2,060,263
Total Liabilities		2,723,292			2,984,576
Home Building [Member] | Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Cash and cash equivalents		94,391			429,977
Receivables		4,192			5,135
Inventories		0			0
Investments in unconsolidated joint ventures		0			0
Property and equipment, net		21,382			18,450
Deferred tax assets, net		78,039			84,564
Other assets		82,905			77,288
Intercompany receivables		3,802,227			3,569,422
Investments in subsidiaries		95,776			67,657
Total assets		280,909			615,414
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		114,162			126,176
Mortgages and notes payable		1,817,428			1,995,115
Total Liabilities		1,931,590			2,121,291
Home Building [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		71,436			114,269
Receivables		225,448			198,465
Inventories		3,496,318			3,314,386
Investments in unconsolidated joint ventures		56,446			61,960
Property and equipment, net		36,420			5,523
Deferred tax assets, net		296,769			303,669
Other assets		2,889			4,007
Intercompany receivables		0			0
Investments in subsidiaries		0			0
Total assets		4,185,726			4,002,279
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		484,752			584,321
Mortgages and notes payable		12,018			40,038
Total Liabilities		496,770			624,359
Home Building [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		13,049			30,113
Receivables		70,068			89,230
Inventories		284,535			268,453
Investments in unconsolidated joint ventures		0			0
Property and equipment, net		3,419			310
Deferred tax assets, net		49,587			53,587
Other assets		1,940			1,805
Intercompany receivables		177,745			158,760
Investments in subsidiaries		0			0
Total assets		422,598			443,498
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		269,822			213,816
Mortgages and notes payable		25,110			25,110
Total Liabilities		294,932			238,926
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		(3,979,972)			(3,728,182)
Investments in subsidiaries		(95,776)			(67,657)
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		888			760	$ 756
Receivables		1,415			2,885
Investments in unconsolidated joint ventures		8,346			8,594
Other assets	[1]	20,071			141
Total assets		30,720		$ 32,108	12,380
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		1,451			1,495
Financial services		1,451			1,495
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		30,720			12,380
Liabilities and stockholders’ equity
Financial services		1,451			1,495
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, 2019 included $19.9 million of contract assets for estimated future renewal commissions due to our adoption of ASC 606 effective December 1, 2018, as described in Note 1 – Basis of Presentation and Significant Accounting Policies.