Supplemental Guarantor Information (Condensed Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended
		Feb. 28, 2018	Feb. 28, 2017
Condensed Consolidated Statements of Operations
Revenues		$ 871,623	$ 818,596
Homebuilding:
Revenues		869,205	816,246
Construction and land costs		(729,478)	(698,080)
Selling, general and administrative expenses		(95,724)	(92,889)
Operating income (loss)		44,003	25,277
Interest income		1,003	198
Interest expense	[1]	0	(6,307)
Intercompany Interest Income (Expense)		0	0
Equity in income of unconsolidated joint ventures		(426)	760
Total pretax income (loss)		46,045	21,459
Income tax expense		(117,300)	(7,200)
Income (Loss) from Subsidiaries, Net of Tax		0	0
Net income (loss)		(71,255)	14,259
KB Home Corporate
Condensed Consolidated Statements of Operations
Revenues		0	0
Homebuilding:
Revenues		0	0
Construction and land costs		0	0
Selling, general and administrative expenses		(22,166)	(22,267)
Operating income (loss)		(22,166)	(22,267)
Interest income		998	197
Interest expense		(37,972)	(48,349)
Intercompany Interest Income (Expense)		72,846	73,493
Total pretax income (loss)		13,706	3,074
Income tax expense		(44,700)	1,300
Income (Loss) from Subsidiaries, Net of Tax		(40,261)	9,885
Net income (loss)		(71,255)	14,259
Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		775,695	729,927
Homebuilding:
Revenues		775,695	729,927
Construction and land costs		(648,119)	(618,452)
Selling, general and administrative expenses		(65,841)	(62,898)
Operating income (loss)		61,735	48,577
Interest income		5	1
Interest expense		(689)	(568)
Intercompany Interest Income (Expense)		(30,499)	(26,603)
Total pretax income (loss)		29,707	22,138
Income tax expense		(48,100)	(8,800)
Income (Loss) from Subsidiaries, Net of Tax		0	0
Net income (loss)		(18,393)	13,338
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		95,928	88,669
Homebuilding:
Revenues		93,510	86,319
Construction and land costs		(81,359)	(79,628)
Selling, general and administrative expenses		(7,717)	(7,724)
Operating income (loss)		4,434	(1,033)
Interest income		0	0
Interest expense		(1,283)	(1,162)
Intercompany Interest Income (Expense)		(2,403)	(3,118)
Total pretax income (loss)		2,632	(3,753)
Income tax expense		(24,500)	300
Income (Loss) from Subsidiaries, Net of Tax		0	0
Net income (loss)		(21,868)	(3,453)
Homebuilding [Member]
Homebuilding:
Equity in income of unconsolidated joint ventures		(845)	731
Total pretax income (loss)		44,161	19,899
Homebuilding [Member] | KB Home Corporate
Homebuilding:
Equity in income of unconsolidated joint ventures		0	0
Total pretax income (loss)		13,706	3,074
Homebuilding [Member] | Guarantor Subsidiaries
Homebuilding:
Equity in income of unconsolidated joint ventures		(845)	731
Total pretax income (loss)		29,707	22,138
Homebuilding [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Equity in income of unconsolidated joint ventures		0	0
Total pretax income (loss)		748	(5,313)
Financial services [Member]
Homebuilding:
Operating income (loss)		1,465	1,531
Equity in income of unconsolidated joint ventures		419	29
Total pretax income (loss)		1,884	1,560
Financial services [Member] | KB Home Corporate
Homebuilding:
Total pretax income (loss)		0	0
Financial services [Member] | Guarantor Subsidiaries
Homebuilding:
Total pretax income (loss)		0	0
Financial services [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Total pretax income (loss)		1,884	1,560
Consolidating Adjustments
Condensed Consolidated Statements of Operations
Revenues		0	0
Homebuilding:
Revenues		0	0
Construction and land costs		0	0
Selling, general and administrative expenses		0	0
Operating income (loss)		0	0
Interest income		0	0
Interest expense		39,944	43,772
Intercompany Interest Income (Expense)		(39,944)	(43,772)
Total pretax income (loss)		0	0
Income tax expense		0	0
Income (Loss) from Subsidiaries, Net of Tax		40,261	(9,885)
Net income (loss)		40,261	(9,885)
Consolidating Adjustments | Homebuilding [Member]
Homebuilding:
Equity in income of unconsolidated joint ventures		0	0
Total pretax income (loss)		0	0
Consolidating Adjustments | Financial services [Member]
Homebuilding:
Total pretax income (loss)		$ 0	$ 0

[1] Interest incurred and interest expensed for the three months ended February 28, 2017 included a charge of $5.7 million for the early extinguishment of debt