Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Feb. 28, 2017	Feb. 29, 2016
Cash flows from operating activities:
Net cash used in operating activities	$ (77,042)	$ (143,313)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(8,750)	(291)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	1,107	0
Purchases of property and equipment, net	(1,015)	(1,413)
Intercompany	0	0
Net cash used in investing activities	(8,658)	(1,704)
Cash flows from financing activities:
Change in restricted cash	0	(4,987)
Repayment of senior notes	(105,326)	0
Payments on mortgages and land contracts due to land sellers and other loans	(45,428)	(5,659)
Issuance of common stock under employee stock plans	662	0
Payments of cash dividends	(2,215)	(2,270)
Stock repurchases	(2,543)	(87,526)
Intercompany	0	0
Net cash used in financing activities	(154,850)	(90,468)
Net decrease in cash and cash equivalents	(240,550)	(235,485)
Cash and cash equivalents at beginning of period	593,000	560,341
Cash and cash equivalents at end of period	352,450	324,856
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities	11,773	13,908
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	0
Purchases of property and equipment, net	(892)	(1,129)
Intercompany	(106,903)	(115,459)
Net cash used in investing activities	(107,795)	(116,588)
Cash flows from financing activities:
Change in restricted cash		(4,987)
Repayment of senior notes	(105,326)
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Issuance of common stock under employee stock plans	662
Payments of cash dividends	(2,215)	(2,270)
Stock repurchases	(2,543)	(87,526)
Intercompany	0	0
Net cash used in financing activities	(109,422)	(84,809)
Net decrease in cash and cash equivalents	(205,444)	(187,489)
Cash and cash equivalents at beginning of period	463,100	444,850
Cash and cash equivalents at end of period	257,656	257,361
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(71,130)	(137,158)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(3,500)	(291)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	1,107
Purchases of property and equipment, net	(113)	(265)
Intercompany	0	0
Net cash used in investing activities	(2,506)	(556)
Cash flows from financing activities:
Change in restricted cash		0
Repayment of senior notes	0
Payments on mortgages and land contracts due to land sellers and other loans	(45,428)	(5,659)
Issuance of common stock under employee stock plans	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	102,302	104,452
Net cash used in financing activities	56,874	98,793
Net decrease in cash and cash equivalents	(16,762)	(38,921)
Cash and cash equivalents at beginning of period	100,439	96,741
Cash and cash equivalents at end of period	83,677	57,820
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(17,685)	(20,063)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(5,250)	0
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	0
Purchases of property and equipment, net	(10)	(19)
Intercompany	0	0
Net cash used in investing activities	(5,260)	(19)
Cash flows from financing activities:
Change in restricted cash		0
Repayment of senior notes	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
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	4,601	11,007
Net cash used in financing activities	4,601	11,007
Net decrease in cash and cash equivalents	(18,344)	(9,075)
Cash and cash equivalents at beginning of period	29,461	18,750
Cash and cash equivalents at end of period	11,117	9,675
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, Dividends or Distributions, Return of Capital	0
Purchases of property and equipment, net	0	0
Intercompany	106,903	115,459
Net cash used in investing activities	106,903	115,459
Cash flows from financing activities:
Change in restricted cash		0
Repayment of senior notes	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
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	(106,903)	(115,459)
Net cash used in financing activities	(106,903)	(115,459)
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