Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Aug. 31, 2016	Aug. 31, 2017	Aug. 31, 2016
Cash flows from operating activities:
Net cash used in operating activities		$ 103,270	$ (102,612)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		(15,154)	(1,000)
Proceeds from Equity Method Investment, Distribution, Return of Capital		8,159	3,495
Purchases of property and equipment, net		(6,643)	(2,680)
Intercompany		0	0
Net cash used in investing activities		(13,638)	(185)
Cash flows from financing activities:
Change in restricted cash		0	(8,742)
Repayment of senior notes		(105,326)	0
Payments of Debt Issuance Costs		(1,711)	0
Payments on mortgages and land contracts due to land sellers and other loans		(92,443)	(41,913)
Issuance of common stock under employee stock plans		20,677	7,351
Payments of cash dividends		(6,479)	(6,471)
Stock repurchases		(2,543)	(87,531)
Intercompany		0	0
Net cash used in financing activities		(187,825)	(119,822)
Net decrease in cash and cash equivalents		(98,193)	(222,619)
Cash and cash equivalents at beginning of period		593,000	560,341
Cash and cash equivalents at end of period	$ 337,722	494,807	337,722
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities		82,480	49,705
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		0	0
Proceeds from Equity Method Investment, Distribution, Return of Capital		0	0
Purchases of property and equipment, net		(5,875)	(2,066)
Intercompany		(43,367)	(141,886)
Net cash used in investing activities		(49,242)	(143,952)
Cash flows from financing activities:
Change in restricted cash			(8,742)
Repayment of senior notes		(105,326)
Payments of Debt Issuance Costs		(1,711)
Payments on mortgages and land contracts due to land sellers and other loans		0	0
Issuance of common stock under employee stock plans		20,677	7,351
Payments of cash dividends		(6,479)	(6,471)
Stock repurchases		(2,543)	(87,531)
Intercompany		0	0
Net cash used in financing activities		(95,382)	(77,909)
Net decrease in cash and cash equivalents		(62,144)	(172,156)
Cash and cash equivalents at beginning of period		463,100	444,850
Cash and cash equivalents at end of period	272,694	400,956	272,694
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities		30,480	(205,084)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		(9,899)	(1,000)
Proceeds from Equity Method Investment, Distribution, Return of Capital		3,169	3,495
Purchases of property and equipment, net		(719)	(452)
Intercompany		0	0
Net cash used in investing activities		(7,449)	2,043
Cash flows from financing activities:
Change in restricted cash			0
Repayment of senior notes		0
Payments of Debt Issuance Costs		0
Payments on mortgages and land contracts due to land sellers and other loans		(92,443)	(41,913)
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends		0	0
Stock repurchases		0	0
Intercompany		51,595	206,168
Net cash used in financing activities		(40,848)	164,255
Net decrease in cash and cash equivalents		(17,817)	(38,786)
Cash and cash equivalents at beginning of period		100,439	96,741
Cash and cash equivalents at end of period	57,955	82,622	57,955
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities		(9,690)	52,767
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		(5,255)	0
Proceeds from Equity Method Investment, Distribution, Return of Capital		4,990	0
Purchases of property and equipment, net		(49)	(162)
Intercompany		0	0
Net cash used in investing activities		(314)	(162)
Cash flows from financing activities:
Change in restricted cash			0
Repayment of senior notes		0
Payments of Debt Issuance Costs		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
Stock repurchases		0	0
Intercompany		(8,228)	(64,282)
Net cash used in financing activities		(8,228)	(64,282)
Net decrease in cash and cash equivalents		(18,232)	(11,677)
Cash and cash equivalents at beginning of period		29,461	18,750
Cash and cash equivalents at end of period	7,073	11,229	7,073
Consolidating Adjustments
Cash flows from operating activities:
Net cash used in operating activities		0	0
Cash flows from investing activities:
Contributions to unconsolidated joint ventures		0	0
Proceeds from Equity Method Investment, Distribution, Return of Capital		0	0
Purchases of property and equipment, net		0	0
Intercompany		43,367	141,886
Net cash used in investing activities		43,367	141,886
Cash flows from financing activities:
Change in restricted cash			0
Repayment of senior notes		0
Payments of Debt Issuance Costs		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
Stock repurchases		0	0
Intercompany		(43,367)	(141,886)
Net cash used in financing activities		(43,367)	(141,886)
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	$ 0