Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Aug. 31, 2014	Aug. 31, 2013
Cash flows from operating activities:
Net cash used in operating activities	$ (716,662)	$ (401,459)
Cash flows from investing activities:
Return of investments in (contributions to) unconsolidated joint ventures	(34,034)	(10,056)
Proceeds from Sale of Equity Method Investments	10,110	0
Purchases of property and equipment, net	(4,158)	(1,359)
Intercompany	0	0
Net cash provided by (used in) investing activities	(28,082)	(11,415)
Cash flows from financing activities:
Change in restricted cash	9,450	731
Proceeds from issuance of debt	400,000	230,000
Payment of debt issuance costs	(5,448)	(10,086)
Payments on mortgages and land contracts due to land sellers and other loans	(23,292)	(44,405)
Proceeds from issuance of common stock, net	137,045	109,503
Issuance of common stock under employee stock plans	202	2,147
Payments of cash dividends	(6,682)	(6,272)
Payments for Repurchase of Common Stock	(46)	(7,967)
Intercompany	0	0
Net cash provided by (used in) financing activities	511,229	273,651
Net increase (decrease) in cash and cash equivalents	(233,515)	(139,223)
Cash and cash equivalents at beginning of period	532,523	525,688
Cash and cash equivalents at end of period	299,008	386,465
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities	65,951	25,657
Cash flows from investing activities:
Return of investments in (contributions to) unconsolidated joint ventures	0	0
Proceeds from Sale of Equity Method Investments	0
Purchases of property and equipment, net	(131)	(346)
Intercompany	(840,539)	(493,419)
Net cash provided by (used in) investing activities	(840,670)	(493,765)
Cash flows from financing activities:
Change in restricted cash	9,450	731
Proceeds from issuance of debt	400,000	230,000
Payment of debt issuance costs	(5,448)	(10,086)
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Proceeds from issuance of common stock, net	137,045	109,503
Issuance of common stock under employee stock plans	202	2,147
Payments of cash dividends	(6,682)	(6,272)
Payments for Repurchase of Common Stock	(46)	(7,967)
Intercompany	0	0
Net cash provided by (used in) financing activities	534,521	318,056
Net increase (decrease) in cash and cash equivalents	(240,198)	(150,052)
Cash and cash equivalents at beginning of period	476,847	457,007
Cash and cash equivalents at end of period	236,649	306,955
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(768,929)	(413,443)
Cash flows from investing activities:
Return of investments in (contributions to) unconsolidated joint ventures	(34,034)	(5,063)
Proceeds from Sale of Equity Method Investments	10,110
Purchases of property and equipment, net	(3,924)	(783)
Intercompany	0	0
Net cash provided by (used in) investing activities	(27,848)	(5,846)
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
Payments on mortgages and land contracts due to land sellers and other loans	(23,292)	(44,405)
Proceeds from issuance of common stock, net	0	0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Payments for Repurchase of Common Stock	0	0
Intercompany	834,483	475,592
Net cash provided by (used in) financing activities	811,191	431,187
Net increase (decrease) in cash and cash equivalents	14,414	11,898
Cash and cash equivalents at beginning of period	41,316	54,205
Cash and cash equivalents at end of period	55,730	66,103
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(13,684)	(13,673)
Cash flows from investing activities:
Return of investments in (contributions to) unconsolidated joint ventures	0	(4,993)
Proceeds from Sale of Equity Method Investments	0
Purchases of property and equipment, net	(103)	(230)
Intercompany	0	0
Net cash provided by (used in) investing activities	(103)	(5,223)
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
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Proceeds from issuance of common stock, net	0	0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Payments for Repurchase of Common Stock	0	0
Intercompany	6,056	17,827
Net cash provided by (used in) financing activities	6,056	17,827
Net increase (decrease) in cash and cash equivalents	(7,731)	(1,069)
Cash and cash equivalents at beginning of period	14,360	14,476
Cash and cash equivalents at end of period	6,629	13,407
Consolidating Adjustments
Cash flows from operating activities:
Net cash used in operating activities	0	0
Cash flows from investing activities:
Return of investments in (contributions to) unconsolidated joint ventures	0	0
Proceeds from Sale of Equity Method Investments	0
Purchases of property and equipment, net	0	0
Intercompany	840,539	493,419
Net cash provided by (used in) investing activities	840,539	493,419
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
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Proceeds from issuance of common stock, net	0	0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Payments for Repurchase of Common Stock	0	0
Intercompany	(840,539)	(493,419)
Net cash provided by (used in) financing activities	(840,539)	(493,419)
Net increase (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