Supplemental Guarantor Information (Condensed Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017
Condensed Consolidated Statements of Operations
Revenues		$ 1,101,423	$ 1,002,794	$ 1,973,046	$ 1,821,390
Homebuilding:
Revenues		1,098,673	1,000,072	1,967,878	1,816,318
Construction and land costs		(911,244)	(846,596)	(1,640,722)	(1,544,676)
Selling, general and administrative expenses		(113,231)	(103,917)	(208,955)	(196,806)
Operating income (loss)		74,198	49,559	118,201	74,836
Interest income		1,278	202	2,281	400
Interest expense	[1]	0	0	0	(6,307)
Intercompany Interest Income (Expense)		0	0	0	0
Equity in income of unconsolidated joint ventures				613	1,075
Total pretax income (loss)		78,308	51,982	124,353	73,441
Income tax expense		(21,000)	(20,200)	(138,300)	(27,400)
Income (Loss) from Subsidiaries, Net of Tax		0	0	0	0
Net income (loss)		57,308	31,782	(13,947)	46,041
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		(26,815)	(23,322)	(48,981)	(45,589)
Operating income (loss)		(26,815)	(23,322)	(48,981)	(45,589)
Interest income		1,181	198	2,179	395
Interest expense		(37,942)	(41,693)	(75,914)	(90,042)
Intercompany Interest Income (Expense)		75,277	75,610	148,123	149,103
Total pretax income (loss)		11,701	10,793	25,407	13,867
Income tax expense		(2,400)	(2,500)	(47,100)	(1,200)
Income (Loss) from Subsidiaries, Net of Tax		48,007	23,489	7,746	33,374
Net income (loss)		57,308	31,782	(13,947)	46,041
Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		995,927	893,561	1,771,622	1,623,488
Homebuilding:
Revenues		995,927	893,561	1,771,622	1,623,488
Construction and land costs		(821,077)	(751,172)	(1,469,196)	(1,369,624)
Selling, general and administrative expenses		(76,986)	(70,929)	(142,827)	(133,827)
Operating income (loss)		97,864	71,460	159,599	120,037
Interest income		4	2	9	3
Interest expense		(634)	(426)	(1,323)	(994)
Intercompany Interest Income (Expense)		(32,816)	(29,862)	(63,315)	(56,465)
Total pretax income (loss)		64,097	40,579	93,804	62,717
Income tax expense		(17,700)	(17,300)	(65,800)	(26,100)
Income (Loss) from Subsidiaries, Net of Tax		0	0	0	0
Net income (loss)		46,397	23,279	28,004	36,617
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		105,496	109,233	201,424	197,902
Homebuilding:
Revenues		102,746	106,511	196,256	192,830
Construction and land costs		(90,167)	(95,424)	(171,526)	(175,052)
Selling, general and administrative expenses		(9,430)	(9,666)	(17,147)	(17,390)
Operating income (loss)		3,149	1,421	7,583	388
Interest income		93	2	93	2
Interest expense		(1,348)	(1,225)	(2,631)	(2,387)
Intercompany Interest Income (Expense)		(2,537)	(2,404)	(4,940)	(5,522)
Total pretax income (loss)		2,510	610	5,142	(3,143)
Income tax expense		(900)	(400)	(25,400)	(100)
Income (Loss) from Subsidiaries, Net of Tax		0	0	0	0
Net income (loss)		1,610	210	(20,258)	(3,243)
Homebuilding [Member]
Homebuilding:
Equity in income of unconsolidated joint ventures		(322)	(596)	(1,167)	135
Total pretax income (loss)		75,154	49,165	119,315	69,064
Homebuilding [Member] | KB Home Corporate
Homebuilding:
Equity in income of unconsolidated joint ventures		0	0	0	0
Total pretax income (loss)		11,701	10,793	25,407	13,867
Homebuilding [Member] | Guarantor Subsidiaries
Homebuilding:
Equity in income of unconsolidated joint ventures		(321)	(595)	(1,166)	136
Total pretax income (loss)		64,097	40,579	93,804	62,717
Homebuilding [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Equity in income of unconsolidated joint ventures		(1)	(1)	(1)	(1)
Total pretax income (loss)		(644)	(2,207)	104	(7,520)
Financial services [Member]
Homebuilding:
Operating income (loss)		1,793	1,906	3,258	3,437
Equity in income of unconsolidated joint ventures		1,361	911	1,780	940
Total pretax income (loss)		3,154	2,817	5,038	4,377
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)		3,154	2,817	5,038	4,377
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		39,924	43,344	79,868	87,116
Intercompany Interest Income (Expense)		(39,924)	(43,344)	(79,868)	(87,116)
Total pretax income (loss)		0	0	0	0
Income tax expense		0	0	0	0
Income (Loss) from Subsidiaries, Net of Tax		(48,007)	(23,489)	(7,746)	(33,374)
Net income (loss)		(48,007)	(23,489)	(7,746)	(33,374)
Consolidating Adjustments | Homebuilding [Member]
Homebuilding:
Equity in income 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