Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Feb. 29, 2020	Feb. 28, 2019
Cash flows from operating activities:
Net cash provided by (used in) operating activities	$ (9,866)	$ (198,210)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(1,668)	(2,527)
Return of investments in unconsolidated joint ventures	500	5,001
Proceeds from sale of building	0	5,804
Purchases of property and equipment, net	(6,671)	(10,025)
Intercompany	0	0
Net cash used in investing activities	(7,839)	(1,747)
Cash flows from financing activities:
Proceeds from issuance of debt	0	405,250
Issuance costs for unsecured revolving credit facility	0	(5,209)
Repayment of senior notes	0	(230,000)
Borrowings under revolving credit facility	0	140,000
Repayments under revolving credit facility	0	(140,000)
Payments on mortgages and land contracts due to land sellers and other loans	0	(28,020)
Issuance of common stock under employee stock plans	8,226	832
Payments of cash dividends	(8,233)	(2,266)
Tax payments associated with stock-based compensation awards	(6,219)	(3,342)
Intercompany	0	0
Net cash provided by (used in) financing activities	(6,226)	137,245
Net decrease in cash and cash equivalents	(23,931)	(62,712)
Cash and cash equivalents at beginning of period	454,858	575,119
Cash and cash equivalents at end of period	430,927	512,407
Guarantor Subsidiaries [Member]
Cash flows from financing activities:
Proceeds from issuance of debt		0
Issuance costs for unsecured revolving credit facility		0
Non-Guarantor Subsidiaries [Member]
Cash flows from financing activities:
Proceeds from issuance of debt		0
Issuance costs for unsecured revolving credit facility		0
Reportable Legal Entities [Member] | KB Home Corporate [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	(21,949)	13,062
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Return of investments in unconsolidated joint ventures	0	0
Proceeds from sale of building		0
Purchases of property and equipment, net	(1,048)	(2,068)
Intercompany	(18,760)	(190,765)
Net cash used in investing activities	(19,808)	(192,833)
Cash flows from financing activities:
Proceeds from issuance of debt		405,250
Issuance costs for unsecured revolving credit facility		(5,209)
Repayment of senior notes		(230,000)
Borrowings under revolving credit facility		140,000
Repayments under revolving credit facility		(140,000)
Payments on mortgages and land contracts due to land sellers and other loans		0
Issuance of common stock under employee stock plans	8,226	832
Payments of cash dividends	(8,233)	(2,266)
Tax payments associated with stock-based compensation awards	(6,219)	(3,342)
Intercompany	0	0
Net cash provided by (used in) financing activities	(6,226)	165,265
Net decrease in cash and cash equivalents	(47,983)	(14,506)
Cash and cash equivalents at beginning of period	357,966	429,977
Cash and cash equivalents at end of period	309,983	415,471
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	31,705	(337,286)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(1,668)	(2,527)
Return of investments in unconsolidated joint ventures	500	5,001
Proceeds from sale of building		5,804
Purchases of property and equipment, net	(4,432)	(2,032)
Intercompany	0	0
Net cash used in investing activities	(5,600)	6,246
Cash flows from financing activities:
Repayment of senior notes		0
Borrowings under revolving credit facility		0
Repayments under revolving credit facility		0
Payments on mortgages and land contracts due to land sellers and other loans		(28,020)
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Tax payments associated with stock-based compensation awards	0	0
Intercompany	1,314	325,137
Net cash provided by (used in) financing activities	1,314	297,117
Net decrease in cash and cash equivalents	27,419	(33,923)
Cash and cash equivalents at beginning of period	65,434	114,269
Cash and cash equivalents at end of period	92,853	80,346
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	(19,622)	126,014
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Return of investments in unconsolidated joint ventures	0	0
Proceeds from sale of building		0
Purchases of property and equipment, net	(1,191)	(5,925)
Intercompany	0	0
Net cash used in investing activities	(1,191)	(5,925)
Cash flows from financing activities:
Repayment of senior notes		0
Borrowings under revolving credit facility		0
Repayments under revolving credit facility		0
Payments on mortgages and land contracts due to land sellers and other loans		0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Tax payments associated with stock-based compensation awards	0	0
Intercompany	17,446	(134,372)
Net cash provided by (used in) financing activities	17,446	(134,372)
Net decrease in cash and cash equivalents	(3,367)	(14,283)
Cash and cash equivalents at beginning of period	31,458	30,873
Cash and cash equivalents at end of period	28,091	16,590
Consolidating Adjustments [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	0	0
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Return of investments in unconsolidated joint ventures	0	0
Proceeds from sale of building		0
Purchases of property and equipment, net	0	0
Intercompany	18,760	190,765
Net cash used in investing activities	18,760	190,765
Cash flows from financing activities:
Proceeds from issuance of debt		0
Issuance costs for unsecured revolving credit facility		0
Repayment of senior notes		0
Borrowings under revolving credit facility		0
Repayments under revolving credit facility		0
Payments on mortgages and land contracts due to land sellers and other loans		0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Tax payments associated with stock-based compensation awards	0	0
Intercompany	(18,760)	(190,765)
Net cash provided by (used in) financing activities	(18,760)	(190,765)
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0