Supplemental Guarantor Information (Condensed Consolidating Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2014
Condensed Consolidated Statements of Operations
Revenues	$ 1,191,942	$ 913,283	$ 811,050	$ 678,371	$ 985,783	$ 843,157	$ 622,969	$ 580,121		$ 3,594,646	$ 3,032,030	$ 2,400,949
Homebuilding:
Revenues										3,582,943	3,020,987	2,389,643
Construction and land costs										(3,041,101)	(2,539,368)	(1,985,651)
Selling, general and administrative expenses										(389,441)	(342,998)	(288,023)
Operating income										152,401	138,621	115,969
Interest income										529	458	443
Interest Expense										(5,900)	(21,856)	(30,750)
Intercompany Interest Income (Expense)										0	0	0
Equity in income (loss) of unconsolidated joint ventures										(5,601)	2,488	1,427
Pretax income (loss)	55,028	53,463	24,797	16,027	69,917	33,954	12,673	10,499		149,315	127,043	94,949
Income tax benefit (expense)									$ 824,200	(43,700)	(42,400)	823,400
Income (Loss) from Subsidiaries, Net of Tax										0	0	0
Net income	$ 37,528	$ 39,363	$ 15,597	$ 13,127	$ 44,017	$ 23,254	$ 9,573	$ 7,799		105,615	84,643	918,349
KB Home Corporate
Condensed Consolidated Statements of Operations
Revenues										0	0	0
Homebuilding:
Revenues										0	0	0
Construction and land costs										0	0	0
Selling, general and administrative expenses										(91,859)	(86,053)	(68,717)
Operating income										(91,859)	(86,053)	(68,717)
Interest income										470	451	432
Interest Expense										(177,329)	(180,701)	(165,485)
Intercompany Interest Income (Expense)										301,432	289,727	287,017
Equity in income (loss) of unconsolidated joint ventures										0	0
Pretax income (loss)										32,714	23,424	53,247
Income tax benefit (expense)										17,200	2,000	215,691
Income (Loss) from Subsidiaries, Net of Tax										55,701	59,219	649,411
Net income										105,615	84,643	918,349
Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues										3,169,545	2,640,678	2,017,170
Homebuilding:
Revenues										3,169,545	2,640,678	2,017,170
Construction and land costs										(2,661,888)	(2,196,228)	(1,658,925)
Selling, general and administrative expenses										(251,384)	(213,292)	(176,795)
Operating income										256,273	231,158	181,450
Interest income										55	6	9
Interest Expense										(3,958)	(6,184)	(6,056)
Intercompany Interest Income (Expense)										(107,388)	(101,540)	(118,901)
Equity in income (loss) of unconsolidated joint ventures										(2,179)	(1,803)
Pretax income (loss)										142,803	121,637	53,953
Income tax benefit (expense)										(52,700)	(46,700)	507,997
Income (Loss) from Subsidiaries, Net of Tax										0	0	0
Net income										90,103	74,937	561,950
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues										425,101	391,352	383,779
Homebuilding:
Revenues										413,398	380,309	372,473
Construction and land costs										(379,213)	(343,140)	(326,726)
Selling, general and administrative expenses										(46,198)	(43,653)	(42,511)
Operating income										(12,013)	(6,484)	3,236
Interest income										4	1	2
Interest Expense										3,946	0	0
Intercompany Interest Income (Expense)										(14,711)	(23,158)	(27,325)
Equity in income (loss) of unconsolidated joint ventures										(2)	(1)
Pretax income (loss)										(26,202)	(18,018)	(12,251)
Income tax benefit (expense)										(8,200)	2,300	99,712
Income (Loss) from Subsidiaries, Net of Tax										0	0	0
Net income										(34,402)	(15,718)	87,461
Homebuilding [Member]
Condensed Consolidated Statements of Operations
Revenues										3,582,943	3,020,987	2,389,643
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures										(2,181)	(1,804)	741
Pretax income (loss)										144,849	115,419	86,403
Homebuilding [Member] | KB Home Corporate
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures												0
Pretax income (loss)										32,714	23,424	53,247
Homebuilding [Member] | Guarantor Subsidiaries
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures												(2,549)
Pretax income (loss)										142,803	121,637	53,953
Homebuilding [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures												3,290
Pretax income (loss)										(30,668)	(29,642)	(20,797)
Financial services [Member]
Homebuilding:
Operating income										7,886	7,332	7,860
Equity in income (loss) of unconsolidated joint ventures										(3,420)	4,292	686
Pretax income (loss)										4,466	11,624	8,546
Financial services [Member] | KB Home Corporate
Homebuilding:
Pretax income (loss)										0	0	0
Financial services [Member] | Guarantor Subsidiaries
Homebuilding:
Pretax income (loss)										0	0	0
Financial services [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Pretax income (loss)										4,466	11,624	8,546
Consolidating Adjustments
Condensed Consolidated Statements of Operations
Revenues										0	0	0
Homebuilding:
Revenues										0	0	0
Construction and land costs										0	0	0
Selling, general and administrative expenses										0	0	0
Operating income										0	0	0
Interest income										0	0	0
Interest Expense										179,333	165,029	140,791
Intercompany Interest Income (Expense)										(179,333)	(165,029)	(140,791)
Equity in income (loss) of unconsolidated joint ventures										0	0
Pretax income (loss)										0	0	0
Income tax benefit (expense)										0	0	0
Income (Loss) from Subsidiaries, Net of Tax										(55,701)	(59,219)	(649,411)
Net income										(55,701)	(59,219)	(649,411)
Consolidating Adjustments | Homebuilding [Member]
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures												0
Pretax income (loss)										0	0	0
Consolidating Adjustments | Financial services [Member]
Homebuilding:
Pretax income (loss)										$ 0	$ 0	$ 0