Supplemental Guarantor Information (Condensed Consolidated Statements of Operations) (Details) - USD ($)		3 Months Ended
		Feb. 28, 2017	Feb. 29, 2016
Condensed Consolidated Statements of Operations
Revenues		$ 818,596,000	$ 678,371,000
Homebuilding:
Revenues		816,246,000	675,742,000
Construction and land costs		(698,080,000)	(568,818,000)
Selling, general and administrative expenses		(92,889,000)	(87,932,000)
Operating income (loss)		25,277,000	18,992,000
Interest income		198,000	152,000
Interest expense	[1]	(6,307,000)	(3,697,000)
Intercompany Interest Income (Expense)		0	0
Equity in income (loss) of unconsolidated joint ventures		760,000	(1,190,000)
Total pretax income (loss)		21,459,000	16,027,000
Income tax expense	[2]	(7,200,000)	(2,900,000)
Income (Loss) from Subsidiaries, Net of Tax		0	0
Net income		14,259,000	13,127,000
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		(22,267,000)	(24,340,000)
Operating income (loss)		(22,267,000)	(24,340,000)
Interest income		197,000	134,000
Interest expense		(48,349,000)	(44,370,000)
Intercompany Interest Income (Expense)		73,493,000	74,043,000
Total pretax income (loss)		3,074,000	5,467,000
Income tax expense		1,300,000	700,000
Income (Loss) from Subsidiaries, Net of Tax		9,885,000	6,960,000
Net income		14,259,000	13,127,000
Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		729,927,000	601,343,000
Homebuilding:
Revenues		729,927,000	601,343,000
Construction and land costs		(618,452,000)	(500,964,000)
Selling, general and administrative expenses		(62,898,000)	(53,464,000)
Operating income (loss)		48,577,000	46,915,000
Interest income		1,000	18,000
Interest expense		(568,000)	(820,000)
Intercompany Interest Income (Expense)		(26,603,000)	(27,508,000)
Total pretax income (loss)		22,138,000	18,002,000
Income tax expense		(8,800,000)	(3,900,000)
Income (Loss) from Subsidiaries, Net of Tax		0	0
Net income		13,338,000	14,102,000
Non-Guarantor Subsidiaries
Condensed Consolidated Statements of Operations
Revenues		88,669,000	77,028,000
Homebuilding:
Revenues		86,319,000	74,399,000
Construction and land costs		(79,628,000)	(67,854,000)
Selling, general and administrative expenses		(7,724,000)	(10,128,000)
Operating income (loss)		(1,033,000)	(3,583,000)
Interest income		0	0
Interest expense		(1,162,000)	(1,061,000)
Intercompany Interest Income (Expense)		(3,118,000)	(3,981,000)
Total pretax income (loss)		(3,753,000)	(7,442,000)
Income tax expense		300,000	300,000
Income (Loss) from Subsidiaries, Net of Tax		0	0
Net income		(3,453,000)	(7,142,000)
Homebuilding [Member]
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		731,000	(603,000)
Total pretax income (loss)		19,899,000	14,844,000
Homebuilding [Member] | KB Home Corporate
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		0	0
Total pretax income (loss)		3,074,000	5,467,000
Homebuilding [Member] | Guarantor Subsidiaries
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		731,000	(603,000)
Total pretax income (loss)		22,138,000	18,002,000
Homebuilding [Member] | Non-Guarantor Subsidiaries
Homebuilding:
Equity in income (loss) of unconsolidated joint ventures		0	0
Total pretax income (loss)		(5,313,000)	(8,625,000)
Financial services [Member]
Homebuilding:
Operating income (loss)		1,531,000	1,770,000
Equity in income (loss) of unconsolidated joint ventures		29,000	(587,000)
Total pretax income (loss)		1,560,000	1,183,000
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)		1,560,000	1,183,000
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		43,772,000	42,554,000
Intercompany Interest Income (Expense)		(43,772,000)	(42,554,000)
Total pretax income (loss)		0	0
Income tax expense		0	0
Income (Loss) from Subsidiaries, Net of Tax		(9,885,000)	(6,960,000)
Net income		(9,885,000)	(6,960,000)
Consolidating Adjustments | Homebuilding [Member]
Homebuilding:
Equity in income (loss) 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] The amount for the three months ended February 28, 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 $1.1 million and $3.3 million for the three months ended February 28, 2017 and February 29, 2016, respectively.