Supplemental Guarantor Information (Condensed Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Condensed Consolidated Statements of Operations
Revenues		$ 1,002,794	$ 811,050	$ 1,821,390	$ 1,489,421
Homebuilding:
Revenues		1,000,072	808,462	1,816,318	1,484,204
Construction and land costs		(846,596)	(688,714)	(1,544,676)	(1,257,532)
Selling, general and administrative expenses		(103,917)	(93,810)	(196,806)	(181,742)
Operating income (loss)		49,559	25,938	74,836	44,930
Interest income		202	134	400	286
Interest expense	[1]	0	(1,970)	(6,307)	(5,667)
Intercompany Interest Income (Expense)		0	0	0	0
Equity in income (loss) of unconsolidated joint ventures				1,075	(2,212)
Total pretax income (loss)		51,982	24,797	73,441	40,824
Income tax expense	[2]	(20,200)	(9,200)	(27,400)	(12,100)
Income (Loss) from Subsidiaries, Net of Tax		0	0	0	0
Net income		31,782	15,597	46,041	28,724
KB Home Corporate
Condensed Consolidated Statements of Operations
Revenues		0	0	0	0
Homebuilding:
Revenues		0	0	0	0
Construction and land costs		0	0	0	0
Selling, general and administrative expenses		(23,322)	(18,976)	(45,589)	(43,316)
Operating income (loss)		(23,322)	(18,976)	(45,589)	(43,316)
Interest income		198	106	395	240
Interest expense		(41,693)	(44,337)	(90,042)	(88,707)
Intercompany Interest Income (Expense)		75,610	75,719	149,103	149,762
Total pretax income (loss)		10,793	12,512	13,867	17,979
Income tax expense		(2,500)	(2,800)	(1,200)	(2,100)
Income (Loss) from Subsidiaries, Net of Tax		23,489	5,885	33,374	12,845
Net income		31,782	15,597	46,041	28,724
Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		893,561	700,768	1,623,488	1,302,111
Homebuilding:
Revenues		893,561	700,768	1,623,488	1,302,111
Construction and land costs		(751,172)	(586,807)	(1,369,624)	(1,087,771)
Selling, general and administrative expenses		(70,929)	(64,010)	(133,827)	(117,474)
Operating income (loss)		71,460	49,951	120,037	96,866
Interest income		2	24	3	42
Interest expense		(426)	(821)	(994)	(1,641)
Intercompany Interest Income (Expense)		(29,862)	(27,479)	(56,465)	(54,987)
Total pretax income (loss)		40,579	20,853	62,717	38,855
Income tax expense		(17,300)	(8,400)	(26,100)	(12,300)
Income (Loss) from Subsidiaries, Net of Tax		0	0	0	0
Net income		23,279	12,453	36,617	26,555
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		109,233	110,282	197,902	187,310
Homebuilding:
Revenues		106,511	107,694	192,830	182,093
Construction and land costs		(95,424)	(101,907)	(175,052)	(169,761)
Selling, general and administrative expenses		(9,666)	(10,824)	(17,390)	(20,952)
Operating income (loss)		1,421	(5,037)	388	(8,620)
Interest income		2	4	2	4
Interest expense		(1,225)	(1,100)	(2,387)	(2,161)
Intercompany Interest Income (Expense)		(2,404)	(3,952)	(5,522)	(7,933)
Total pretax income (loss)		610	(8,568)	(3,143)	(16,010)
Income tax expense		(400)	2,000	(100)	2,300
Income (Loss) from Subsidiaries, Net of Tax		0	0	0	0
Net income		210	(6,568)	(3,243)	(13,710)
Homebuilding [Member]
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		(596)	(825)	135	(1,428)
Total pretax income (loss)		49,165	23,277	69,064	38,121
Homebuilding [Member] | KB Home Corporate
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		0	0	0	0
Total pretax income (loss)		10,793	12,512	13,867	17,979
Homebuilding [Member] | Guarantor Subsidiaries
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		(595)	(822)	136	(1,425)
Total pretax income (loss)		40,579	20,853	62,717	38,855
Homebuilding [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		(1)	(3)	(1)	(3)
Total pretax income (loss)		(2,207)	(10,088)	(7,520)	(18,713)
Financial services [Member]
Homebuilding:
Operating income (loss)		1,906	1,717	3,437	3,487
Equity in income (loss) of unconsolidated joint ventures		911	(197)	940	(784)
Total pretax income (loss)		2,817	1,520	4,377	2,703
Financial services [Member] | KB Home Corporate
Homebuilding:
Total pretax income (loss)		0	0	0	0
Financial services [Member] | Guarantor Subsidiaries
Homebuilding:
Total pretax income (loss)		0	0	0	0
Financial services [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Total pretax income (loss)		2,817	1,520	4,377	2,703
Consolidating Adjustments
Condensed Consolidated Statements of Operations
Revenues		0	0	0	0
Homebuilding:
Revenues		0	0	0	0
Construction and land costs		0	0	0	0
Selling, general and administrative expenses		0	0	0	0
Operating income (loss)		0	0	0	0
Interest income		0	0	0	0
Interest expense		43,344	44,288	87,116	86,842
Intercompany Interest Income (Expense)		(43,344)	(44,288)	(87,116)	(86,842)
Total pretax income (loss)		0	0	0	0
Income tax expense		0	0	0	0
Income (Loss) from Subsidiaries, Net of Tax		(23,489)	(5,885)	(33,374)	(12,845)
Net income		(23,489)	(5,885)	(33,374)	(12,845)
Consolidating Adjustments | Homebuilding [Member]
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		0	0	0	0
Total pretax income (loss)		0	0	0	0
Consolidating Adjustments | Financial services [Member]
Homebuilding:
Total pretax income (loss)		$ 0	$ 0	$ 0	$ 0

[1] Interest incurred and interest expensed for the six months ended May 31, 2017 included a charge of $5.7 million for the early extinguishment of debt

[2] (a) Amounts reflect the favorable net impact of federal energy tax credits we earned from building energy-efficient homes. The net impact of these tax credits was $.1 million and $.4 million for the three months ended May 31, 2017 and 2016, respectively, and $1.2 million and $3.7 million for the six months ended May 31, 2017 and 2016, respectively.