Supplemental Guarantor Information (Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		Feb. 28, 2018	Nov. 30, 2017	Feb. 28, 2017	Nov. 30, 2016
Assets
Cash and Cash Equivalents, at Carrying Value		$ 560,806	$ 720,861	$ 352,450	$ 593,000
Receivables		250,472	244,213
Inventory, Operative Builders		3,441,574	3,263,386
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		68,176	64,794
Deferred tax assets, net		516,569	633,637
Other assets		108,498	102,498
Investments in and Advances to Affiliates, Amount of Equity		0	0
Total assets		4,957,101	5,041,515
Due from Affiliates		0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		743,912	789,393
Mortgages and notes payable		2,359,570	2,324,845
Financial services		897	966
Due to Affiliate		0	0
Stockholders' equity		1,852,722	1,926,311
Total liabilities and stockholders’ equity		4,957,101	5,041,515
KB Home Corporate
Assets
Cash and Cash Equivalents, at Carrying Value		455,629	575,193	257,656	463,100
Receivables		4,309	24,815
Inventory, Operative Builders		0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0	0
Deferred tax assets, net		206,206	250,747
Other assets		97,950	91,592
Investments in and Advances to Affiliates, Amount of Equity		84,467	49,776
Total assets		4,309,607	4,406,360
Due from Affiliates		3,461,046	3,414,237
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		136,816	163,984
Mortgages and notes payable		2,290,922	2,289,532
Financial services		0	0
Due to Affiliate		29,147	26,533
Stockholders' equity		1,852,722	1,926,311
Total liabilities and stockholders’ equity		4,309,607	4,406,360
Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value		72,731	102,661	83,677	100,439
Receivables		170,217	144,076
Inventory, Operative Builders		3,100,304	2,929,466
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		65,672	62,290
Deferred tax assets, net		195,606	243,523
Other assets		8,109	8,424
Investments in and Advances to Affiliates, Amount of Equity		0	0
Total assets		3,612,639	3,490,440
Due from Affiliates		0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		364,322	371,909
Mortgages and notes payable		43,541	9,283
Financial services		0	0
Due to Affiliate		3,175,070	3,109,248
Stockholders' equity		29,706	0
Total liabilities and stockholders’ equity		3,612,639	3,490,440
Non-Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value		32,446	43,007	11,117	29,461
Receivables		75,946	75,322
Inventory, Operative Builders		341,270	333,920
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		2,504	2,504
Deferred tax assets, net		114,757	139,367
Other assets		2,439	2,482
Investments in and Advances to Affiliates, Amount of Equity		0	0
Total assets		701,163	716,720
Due from Affiliates		120,795	107,992
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		242,774	253,500
Mortgages and notes payable		25,107	26,030
Financial services		897	966
Due to Affiliate		377,624	386,448
Stockholders' equity		54,761	49,776
Total liabilities and stockholders’ equity		701,163	716,720
Homebuilding [Member]
Assets
Cash and Cash Equivalents, at Carrying Value		560,255	720,630	351,880
Total assets		4,945,544	5,029,158
Liabilities and stockholders' equity
Total Liabilities Homebuilding		3,103,482	3,114,238
Homebuilding [Member] | KB Home Corporate
Assets
Cash and Cash Equivalents, at Carrying Value		455,629	575,193
Total assets		764,094	942,347
Liabilities and stockholders' equity
Total Liabilities Homebuilding		2,427,738	2,453,516
Homebuilding [Member] | Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value		72,731	102,661
Total assets		3,612,639	3,490,440
Liabilities and stockholders' equity
Total Liabilities Homebuilding		407,863	381,192
Homebuilding [Member] | Non-Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value		31,895	42,776
Total assets		568,811	596,371
Liabilities and stockholders' equity
Total Liabilities Homebuilding		267,881	279,530
Financial services [Member]
Assets
Cash and Cash Equivalents, at Carrying Value		551	231	570
Receivables		1,489	1,724
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	[1]	9,460	10,340
Other assets		57	62
Total assets		11,557	12,357
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		897	966
Financial services [Member] | KB Home Corporate
Assets
Total assets		0	0
Financial services [Member] | Guarantor Subsidiaries
Assets
Total assets		0	0
Financial services [Member] | Non-Guarantor Subsidiaries
Assets
Total assets		11,557	12,357
Consolidating Adjustments
Assets
Cash and Cash Equivalents, at Carrying Value		0	0	$ 0	$ 0
Receivables		0	0
Inventory, Operative Builders		0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0	0
Deferred tax assets, net		0	0
Other assets		0	0
Investments in and Advances to Affiliates, Amount of Equity		(84,467)	(49,776)
Total assets		(3,666,308)	(3,572,005)
Due from Affiliates		(3,581,841)	(3,522,229)
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities		0	0
Mortgages and notes payable		0	0
Financial services		0	0
Due to Affiliate		(3,581,841)	(3,522,229)
Stockholders' equity		(84,467)	(49,776)
Total liabilities and stockholders’ equity		(3,666,308)	(3,572,005)
Consolidating Adjustments | Homebuilding [Member]
Assets
Cash and Cash Equivalents, at Carrying Value		0	0
Total assets		0	0
Liabilities and stockholders' equity
Total Liabilities Homebuilding		0	0
Consolidating Adjustments | Financial services [Member]
Assets
Total assets		$ 0	$ 0

[1] February 28, 2018 November 30, 2017Assets Cash and cash equivalents$551 $231Receivables 1,489 1,724Investments in unconsolidated joint ventures 9,460 10,340Other assets57 62Total assets$11,557 $12,357Liabilities Accounts payable and accrued expenses$897 $966Total liabilities$897 $966