Supplemental Guarantor Information (Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		Feb. 28, 2019	Dec. 01, 2018	Nov. 30, 2018	Feb. 28, 2018	Nov. 30, 2017
Assets
Cash and cash equivalents		$ 512,407		$ 575,119	$ 560,806	$ 720,861
Receivables		313,609		292,830
Inventories		3,683,763		3,582,839
Investments in unconsolidated joint ventures		57,134		61,960
Property and equipment, net		55,330		24,283
Other assets		89,560		83,100
Total assets		5,173,656		5,073,571
Liabilities and stockholders’ equity
Mortgages and notes payable		2,203,589		2,060,263
Intercompany payables		0		0
Stockholders’ equity		2,128,497		2,087,500	1,852,722	1,926,311
Total liabilities and stockholders’ equity		5,173,656		5,073,571
Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Cash and cash equivalents		415,471		429,977	455,629	575,193
Total assets		4,465,807		4,252,493
Liabilities and stockholders’ equity
Intercompany payables		48,688		43,702
Stockholders’ equity		2,128,497		2,087,500
Total liabilities and stockholders’ equity		4,465,807		4,252,493
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		80,346		114,269	75,325	104,120
Total assets		4,136,910		4,002,279
Liabilities and stockholders’ equity
Intercompany payables		3,666,215		3,377,920
Stockholders’ equity		15,408		0
Total liabilities and stockholders’ equity		4,136,910		4,002,279
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		16,590		30,873	29,852	41,548
Total assets		606,217		614,638
Liabilities and stockholders’ equity
Intercompany payables		216,335		306,560
Stockholders’ equity		88,632		67,657
Total liabilities and stockholders’ equity		606,217		614,638
Consolidating Adjustments [Member]
Assets
Cash and cash equivalents		0		0	0	$ 0
Total assets		(4,035,278)		(3,795,839)
Liabilities and stockholders’ equity
Intercompany payables		(3,931,238)		(3,728,182)
Stockholders’ equity		(104,040)		(67,657)
Total liabilities and stockholders’ equity		(4,035,278)		(3,795,839)
Home Building [Member]
Assets
Cash and cash equivalents		511,690		574,359	560,255
Receivables		313,609		292,830
Inventories		3,683,763	$ 3,547,551	3,582,839
Investments in unconsolidated joint ventures		57,134		61,960
Property and equipment, net		55,330	55,477	24,283
Deferred tax assets, net		433,295	437,796	441,820
Other assets		89,560		83,100
Intercompany receivables		0		0
Investments in subsidiaries		0		0
Total assets		5,144,381		5,061,191
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		840,396		924,313
Mortgages and notes payable		2,203,589		2,060,263
Total Liabilities		3,043,985		2,984,576
Home Building [Member] | Reportable Legal Entities [Member] | KB Home Corporate [Member]
Assets
Cash and cash equivalents		415,471		429,977
Receivables		4,291		5,135
Inventories		0		0
Investments in unconsolidated joint ventures		0		0
Property and equipment, net		20,363		18,450
Deferred tax assets, net		80,339		84,564
Other assets		84,083		77,288
Intercompany receivables		3,757,220		3,569,422
Investments in subsidiaries		104,040		67,657
Total assets		604,547		615,414
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		122,161		126,176
Mortgages and notes payable		2,166,461		1,995,115
Total Liabilities		2,288,622		2,121,291
Home Building [Member] | Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		80,346		114,269
Receivables		228,879		198,465
Inventories		3,435,361		3,314,386
Investments in unconsolidated joint ventures		57,134		61,960
Property and equipment, net		32,002		5,523
Deferred tax assets, net		299,769		303,669
Other assets		3,419		4,007
Intercompany receivables		0		0
Investments in subsidiaries		0		0
Total assets		4,136,910		4,002,279
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		443,269		584,321
Mortgages and notes payable		12,018		40,038
Total Liabilities		455,287		624,359
Home Building [Member] | Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents		15,873		30,113
Receivables		80,439		89,230
Inventories		248,402		268,453
Investments in unconsolidated joint ventures		0		0
Property and equipment, net		2,965		310
Deferred tax assets, net		53,187		53,587
Other assets		2,058		1,805
Intercompany receivables		174,018		158,760
Investments in subsidiaries		0		0
Total assets		402,924		443,498
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		274,966		213,816
Mortgages and notes payable		25,110		25,110
Total Liabilities		300,076		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		(3,931,238)		(3,728,182)
Investments in subsidiaries		(104,040)		(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		717		760	$ 551
Receivables		1,602		2,885
Investments in unconsolidated joint ventures		6,995		8,594
Other assets	[1]	19,961		141
Total assets		29,275	$ 32,108	12,380
Liabilities and stockholders’ equity
Accounts payable and accrued expenses		1,174		1,495
Financial services		1,174		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		29,275		12,380
Liabilities and stockholders’ equity
Financial services		1,174		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 February 28, 2019 included $19.8 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.