Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	May 31, 2017	May 31, 2016
Cash flows from operating activities:
Net cash used in operating activities	$ (64,580)	$ (167,459)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(11,105)	(750)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	6,958	0
Purchases of property and equipment, net	(4,100)	(2,876)
Intercompany	0	0
Net cash used in investing activities	(8,247)	(3,626)
Cash flows from financing activities:
Change in restricted cash	0	(5,827)
Repayment of senior notes	(105,326)	0
Payments on mortgages and land contracts due to land sellers and other loans	(61,640)	(26,639)
Issuance of common stock under employee stock plans	3,049	0
Payments of cash dividends	(4,341)	(4,364)
Stock repurchases	(2,543)	(87,531)
Intercompany	0	0
Net cash used in financing activities	(170,801)	(112,707)
Net decrease in cash and cash equivalents	(243,628)	(283,792)
Cash and cash equivalents at beginning of period	593,000	560,341
Cash and cash equivalents at end of period	349,372	276,549
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities	24,724	6,508
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	(3,724)	(2,437)
Intercompany	(77,681)	(167,470)
Net cash used in investing activities	(81,405)	(169,907)
Cash flows from financing activities:
Change in restricted cash		(5,827)
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	3,049
Payments of cash dividends	(4,341)	(4,364)
Stock repurchases	(2,543)	(87,531)
Intercompany	0	0
Net cash used in financing activities	(109,161)	(86,068)
Net decrease in cash and cash equivalents	(165,842)	(249,467)
Cash and cash equivalents at beginning of period	463,100	444,850
Cash and cash equivalents at end of period	297,258	195,383
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(83,371)	(215,372)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(5,852)	(750)
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	1,969
Purchases of property and equipment, net	(344)	(331)
Intercompany	0	0
Net cash used in investing activities	(4,227)	(1,081)
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	(61,640)	(26,639)
Issuance of common stock under employee stock plans	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	91,185	209,197
Net cash used in financing activities	29,545	182,558
Net decrease in cash and cash equivalents	(58,053)	(33,895)
Cash and cash equivalents at beginning of period	100,439	96,741
Cash and cash equivalents at end of period	42,386	62,846
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(5,933)	41,405
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(5,253)	0
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	4,989
Purchases of property and equipment, net	(32)	(108)
Intercompany	0	0
Net cash used in investing activities	(296)	(108)
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	(13,504)	(41,727)
Net cash used in financing activities	(13,504)	(41,727)
Net decrease in cash and cash equivalents	(19,733)	(430)
Cash and cash equivalents at beginning of period	29,461	18,750
Cash and cash equivalents at end of period	9,728	18,320
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	77,681	167,470
Net cash used in investing activities	77,681	167,470
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	(77,681)	(167,470)
Net cash used in financing activities	(77,681)	(167,470)
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