Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($)	12 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2014
Condensed Consolidated Statements of Cash Flows
Net cash provided by (used in) operating activities	$ 188,655,000	$ 181,185,000	$ (630,691,000)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(5,602,000)	(20,626,000)	(49,097,000)
Proceeds from sale of investment in unconsolidated joint venture	0	0	10,110,000
Return of investments in unconsolidated joint ventures	4,307,000	14,000,000	0
Purchases of property and equipment, net	(4,784,000)	(4,677,000)	(5,795,000)
Intercompany	0	0	0
Net cash used in investing activities	(6,079,000)	(11,303,000)	(44,782,000)
Cash flows from financing activities:
Change in restricted cash	9,344,000	17,891,000	14,671,000
Proceeds from issuance of debt	0	250,000,000	400,000,000
Payment of debt issuance costs	0	(4,561,000)	(5,448,000)
Repayment of senior notes	0	(199,906,000)	0
Payments on mortgages and land contracts due to land sellers and other loans	(67,845,000)	(22,877,000)	(36,918,000)
Proceeds from issuance of common stock, net	0	0	137,045,000
Issuance of common stock under employee stock plans	5,343,000	740,000	1,896,000
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	186,000	157,000	0
Payments of cash dividends	(8,586,000)	(9,186,000)	(8,982,000)
Stock repurchases	(88,359,000)	(567,000)	(546,000)
Intercompany	0	0	0
Net cash provided by (used in) financing activities	(149,917,000)	31,691,000	501,718,000
Net increase (decrease) in cash and cash equivalents	32,659,000	201,573,000	(173,755,000)
Cash and cash equivalents at beginning of year	560,341,000	358,768,000	532,523,000
Cash and cash equivalents at end of year	593,000,000	560,341,000	358,768,000
KB Home Corporate
Condensed Consolidated Statements of Cash Flows
Net cash provided by (used in) operating activities	(40,277,000)	44,422,000	82,629,000
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0	0
Proceeds from sale of investment in unconsolidated joint venture			0
Return of investments in unconsolidated joint ventures	0	0
Purchases of property and equipment, net	(4,052,000)	(2,890,000)	(208,000)
Intercompany	144,651,000	45,470,000	(794,624,000)
Net cash used in investing activities	140,599,000	42,580,000	(794,832,000)
Cash flows from financing activities:
Change in restricted cash	9,344,000	17,891,000	14,671,000
Proceeds from issuance of debt		250,000,000	400,000,000
Payment of debt issuance costs		(4,561,000)	(5,448,000)
Repayment of senior notes		(199,906,000)
Payments on mortgages and land contracts due to land sellers and other loans	0	0	0
Proceeds from issuance of common stock, net			137,045,000
Issuance of common stock under employee stock plans	5,343,000	740,000	1,896,000
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	186,000	157,000
Payments of cash dividends	(8,586,000)	(9,186,000)	(8,982,000)
Stock repurchases	(88,359,000)	(567,000)	(546,000)
Intercompany	0	0	0
Net cash provided by (used in) financing activities	(82,072,000)	54,568,000	538,636,000
Net increase (decrease) in cash and cash equivalents	18,250,000	141,570,000	(173,567,000)
Cash and cash equivalents at beginning of year	444,850,000	303,280,000	476,847,000
Cash and cash equivalents at end of year	463,100,000	444,850,000	303,280,000
Guarantor Subsidiaries
Condensed Consolidated Statements of Cash Flows
Net cash provided by (used in) operating activities	188,372,000	110,688,000	(641,728,000)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(4,852,000)	(20,625,000)	(48,846,000)
Proceeds from sale of investment in unconsolidated joint venture			0
Return of investments in unconsolidated joint ventures	4,307,000	14,000,000
Purchases of property and equipment, net	(555,000)	(1,271,000)	(4,145,000)
Intercompany	0	0	0
Net cash used in investing activities	(1,100,000)	(7,896,000)	(52,991,000)
Cash flows from financing activities:
Change in restricted cash	0	0	0
Proceeds from issuance of debt		0	0
Payment of debt issuance costs		0	0
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	(67,845,000)	(22,877,000)	(36,918,000)
Proceeds from issuance of common stock, net			0
Issuance of common stock under employee stock plans	0	0	0
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	0	0
Payments of cash dividends	0	0	0
Stock repurchases	0	0	0
Intercompany	(115,729,000)	(19,586,000)	730,719,000
Net cash provided by (used in) financing activities	(183,574,000)	(42,463,000)	693,801,000
Net increase (decrease) in cash and cash equivalents	3,698,000	60,329,000	(918,000)
Cash and cash equivalents at beginning of year	96,741,000	36,412,000	37,330,000
Cash and cash equivalents at end of year	100,439,000	96,741,000	36,412,000
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Cash Flows
Net cash provided by (used in) operating activities	40,560,000	26,075,000	(71,592,000)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(750,000)	(1,000)	(251,000)
Proceeds from sale of investment in unconsolidated joint venture			10,110,000
Return of investments in unconsolidated joint ventures	0	0
Purchases of property and equipment, net	(177,000)	(516,000)	(1,442,000)
Intercompany	0	0	0
Net cash used in investing activities	(927,000)	(517,000)	8,417,000
Cash flows from financing activities:
Change in restricted cash	0	0	0
Proceeds from issuance of debt		0	0
Payment of debt issuance costs		0	0
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	0	0	0
Proceeds from issuance of common stock, net			0
Issuance of common stock under employee stock plans	0	0	0
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	0	0
Payments of cash dividends	0	0	0
Stock repurchases	0	0	0
Intercompany	(28,922,000)	(25,884,000)	63,905,000
Net cash provided by (used in) financing activities	(28,922,000)	(25,884,000)	63,905,000
Net increase (decrease) in cash and cash equivalents	10,711,000	(326,000)	730,000
Cash and cash equivalents at beginning of year	18,750,000	19,076,000	18,346,000
Cash and cash equivalents at end of year	29,461,000	18,750,000	19,076,000
Consolidating Adjustments
Condensed Consolidated Statements of Cash Flows
Net cash provided by (used in) operating activities	0	0	0
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0	0
Proceeds from sale of investment in unconsolidated joint venture			0
Return of investments in unconsolidated joint ventures	0	0
Purchases of property and equipment, net	0	0	0
Intercompany	(144,651,000)	(45,470,000)	794,624,000
Net cash used in investing activities	(144,651,000)	(45,470,000)	794,624,000
Cash flows from financing activities:
Change in restricted cash	0	0	0
Proceeds from issuance of debt		0	0
Payment of debt issuance costs		0	0
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	0	0	0
Proceeds from issuance of common stock, net			0
Issuance of common stock under employee stock plans	0	0	0
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	0	0
Payments of cash dividends	0	0	0
Stock repurchases	0	0	0
Intercompany	144,651,000	45,470,000	(794,624,000)
Net cash provided by (used in) financing activities	144,651,000	45,470,000	(794,624,000)
Net increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of year	0	0	0
Cash and cash equivalents at end of year	$ 0	$ 0	$ 0