Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	9 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Cash flows from operating activities:
Net cash used in operating activities	$ (22,084)	$ (716,662)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(20,955)	(34,034)
Proceeds from sale of investment in unconsolidated joint venture	0	10,110
Return of investments in unconsolidated joint ventures	14,000	0
Purchases of property and equipment, net	(2,100)	(4,158)
Intercompany	0	0
Net cash used in investing activities	(9,055)	(28,082)
Cash flows from financing activities:
Change in restricted cash	2,207	9,450
Proceeds from issuance of debt	250,000	400,000
Payment of debt issuance costs	(4,561)	(5,448)
Repayment of senior notes	(199,906)	0
Payments on mortgages and land contracts due to land sellers and other loans	(13,736)	(23,292)
Proceeds from issuance of common stock, net	0	137,045
Issuance of common stock under employee stock plans	436	202
Payments of cash dividends	(6,890)	(6,682)
Stock repurchases	(300)	(46)
Intercompany	0	0
Net cash provided by financing activities	27,250	511,229
Net decrease in cash and cash equivalents	(3,889)	(233,515)
Cash and cash equivalents at beginning of period	358,768	532,523
Cash and cash equivalents at end of period	354,879	299,008
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities	41,620	66,251
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Proceeds from sale of investment in unconsolidated joint venture		0
Return of investments in unconsolidated joint ventures	0
Purchases of property and equipment, net	(498)	(131)
Intercompany	(96,519)	(840,839)
Net cash used in investing activities	(97,017)	(840,970)
Cash flows from financing activities:
Change in restricted cash	2,207	9,450
Proceeds from issuance of debt	250,000	400,000
Payment of debt issuance costs	(4,561)	(5,448)
Repayment of senior notes	(199,906)
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Proceeds from issuance of common stock, net		137,045
Issuance of common stock under employee stock plans	436	202
Payments of cash dividends	(6,890)	(6,682)
Stock repurchases	(300)	(46)
Intercompany	0	0
Net cash provided by financing activities	40,986	534,521
Net decrease in cash and cash equivalents	(14,411)	(240,198)
Cash and cash equivalents at beginning of period	303,280	476,847
Cash and cash equivalents at end of period	288,869	236,649
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(43,447)	(730,397)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(20,954)	(33,786)
Proceeds from sale of investment in unconsolidated joint venture		0
Return of investments in unconsolidated joint ventures	14,000
Purchases of property and equipment, net	(1,565)	(3,499)
Intercompany	0	0
Net cash used in investing activities	(8,519)	(37,285)
Cash flows from financing activities:
Change in restricted cash	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	(13,736)	(23,292)
Proceeds from issuance of common stock, net		0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	87,849	804,809
Net cash provided by financing activities	74,113	781,517
Net decrease in cash and cash equivalents	22,147	13,835
Cash and cash equivalents at beginning of period	38,124	39,952
Cash and cash equivalents at end of period	60,271	53,787
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(20,257)	(52,516)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(1)	(248)
Proceeds from sale of investment in unconsolidated joint venture		10,110
Return of investments in unconsolidated joint ventures	0
Purchases of property and equipment, net	(37)	(528)
Intercompany	0	0
Net cash used in investing activities	(38)	9,334
Cash flows from financing activities:
Change in restricted cash	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
Proceeds from issuance of common stock, net		0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	8,670	36,030
Net cash provided by financing activities	8,670	36,030
Net decrease in cash and cash equivalents	(11,625)	(7,152)
Cash and cash equivalents at beginning of period	17,364	15,724
Cash and cash equivalents at end of period	5,739	8,572
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 sale of investment in unconsolidated joint venture		0
Return of investments in unconsolidated joint ventures	0
Purchases of property and equipment, net	0	0
Intercompany	96,519	840,839
Net cash used in investing activities	96,519	840,839
Cash flows from financing activities:
Change in restricted cash	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
Proceeds from issuance of common stock, net		0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	(96,519)	(840,839)
Net cash provided by financing activities	(96,519)	(840,839)
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