Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	May 31, 2018	May 31, 2017
Cash flows from operating activities:
Net cash used in operating activities	$ (19,369)	$ (64,580)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(11,600)	(11,105)
Proceeds from Equity Method Investment, Distribution, Return of Capital	1,099	6,958
Purchases of property and equipment, net	(3,427)	(4,100)
Intercompany	0	0
Net cash used in investing activities	(13,928)	(8,247)
Cash flows from financing activities:
Repayment of senior notes		(105,326)
Payments on mortgages and land contracts due to land sellers and other loans	(10,494)	(61,640)
Issuance of common stock under employee stock plans	4,771	3,049
Payments of cash dividends	(4,500)	(4,341)
Stock repurchases	(6,787)	(2,543)
Intercompany	0	0
Net cash used in financing activities	(17,010)	(170,801)
Net decrease in cash and cash equivalents	(50,307)	(243,628)
Cash and cash equivalents at beginning of period	720,861	593,000
Cash and cash equivalents at end of period	670,554	349,372
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities	18,931	24,724
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	(3,102)	(3,724)
Intercompany	(42,380)	(77,681)
Net cash used in investing activities	(45,482)	(81,405)
Cash flows from financing activities:
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	4,771	3,049
Payments of cash dividends	(4,500)	(4,341)
Stock repurchases	(6,787)	(2,543)
Intercompany	0	0
Net cash used in financing activities	(6,516)	(109,161)
Net decrease in cash and cash equivalents	(33,067)	(165,842)
Cash and cash equivalents at beginning of period	575,193	463,100
Cash and cash equivalents at end of period	542,126	297,258
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(33,782)	(83,371)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(11,600)	(5,852)
Proceeds from Equity Method Investment, Distribution, Return of Capital	1,099	1,969
Purchases of property and equipment, net	(277)	(344)
Intercompany	0	0
Net cash used in investing activities	(10,778)	(4,227)
Cash flows from financing activities:
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	(9,574)	(61,640)
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	45,421	91,185
Net cash used in financing activities	35,847	29,545
Net decrease in cash and cash equivalents	(8,713)	(58,053)
Cash and cash equivalents at beginning of period	102,661	100,439
Cash and cash equivalents at end of period	93,948	42,386
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(4,518)	(5,933)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	(5,253)
Proceeds from Equity Method Investment, Distribution, Return of Capital	0	4,989
Purchases of property and equipment, net	(48)	(32)
Intercompany	0	0
Net cash used in investing activities	(48)	(296)
Cash flows from financing activities:
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	(920)	0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	(3,041)	(13,504)
Net cash used in financing activities	(3,961)	(13,504)
Net decrease in cash and cash equivalents	(8,527)	(19,733)
Cash and cash equivalents at beginning of period	43,007	29,461
Cash and cash equivalents at end of period	34,480	9,728
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	42,380	77,681
Net cash used in investing activities	42,380	77,681
Cash flows from financing activities:
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	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	(42,380)	(77,681)
Net cash used in financing activities	(42,380)	(77,681)
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