Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands		3 Months Ended
	Feb. 20, 2019	Feb. 28, 2019	Feb. 28, 2018
Cash flows from operating activities:
Net cash provided by (used in) operating activities		$ (198,210)	$ (141,680)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		(2,527)	(8,025)
Return of investments in unconsolidated joint ventures		5,001	1,099
Proceeds from sale of building		5,804	0
Purchases of property and equipment, net		(10,025)	(1,924)
Intercompany		0	0
Net cash used in investing activities		(1,747)	(8,850)
Cash flows from financing activities:
Proceeds from issuance of debt	$ 400,000	405,250	0
Issuance costs for unsecured revolving credit facility		(5,209)	0
Repayment of senior notes		(230,000)	0
Borrowings under revolving credit facility		140,000	0
Repayments under revolving credit facility		(140,000)	0
Payments on mortgages and land contracts due to land sellers and other loans		(28,020)	(3,362)
Issuance of common stock under employee stock plans		832	2,946
Payments of cash dividends		(2,266)	(2,322)
Tax payments associated with stock-based compensation awards		(3,342)	(6,787)
Intercompany		0	0
Net cash provided by (used in) financing activities		137,245	(9,525)
Net decrease in cash and cash equivalents		(62,712)	(160,055)
Cash and cash equivalents at beginning of period		575,119	720,861
Cash and cash equivalents at end of period		512,407	560,806
Reportable Legal Entities [Member] | KB Home Corporate [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities		13,062	3,066
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		(2,068)	(1,776)
Intercompany		(190,765)	(114,691)
Net cash used in investing activities		(192,833)	(116,467)
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	0
Issuance of common stock under employee stock plans		832	2,946
Payments of cash dividends		(2,266)	(2,322)
Tax payments associated with stock-based compensation awards		(3,342)	(6,787)
Intercompany		0	0
Net cash provided by (used in) financing activities		165,265	(6,163)
Net decrease in cash and cash equivalents		(14,506)	(119,564)
Cash and cash equivalents at beginning of period		429,977	575,193
Cash and cash equivalents at end of period		415,471	455,629
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities		(337,286)	(137,254)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		(2,527)	(8,025)
Return of investments in unconsolidated joint ventures		5,001	1,099
Proceeds from sale of building		5,804
Purchases of property and equipment, net		(2,032)	(177)
Intercompany		0	0
Net cash used in investing activities		6,246	(7,103)
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		(28,020)	(2,442)
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		325,137	118,004
Net cash provided by (used in) financing activities		297,117	115,562
Net decrease in cash and cash equivalents		(33,923)	(28,795)
Cash and cash equivalents at beginning of period		114,269	104,120
Cash and cash equivalents at end of period		80,346	75,325
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities		126,014	(7,492)
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		(5,925)	29
Intercompany		0	0
Net cash used in investing activities		(5,925)	29
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	(920)
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		(134,372)	(3,313)
Net cash provided by (used in) financing activities		(134,372)	(4,233)
Net decrease in cash and cash equivalents		(14,283)	(11,696)
Cash and cash equivalents at beginning of period		30,873	41,548
Cash and cash equivalents at end of period		16,590	29,852
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		190,765	114,691
Net cash used in investing activities		190,765	114,691
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	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		(190,765)	(114,691)
Net cash provided by (used in) financing activities		(190,765)	(114,691)
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