Supplemental Guarantor Information (Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Aug. 31, 2018	Nov. 30, 2017	Aug. 31, 2017	Nov. 30, 2016
Assets
Cash and Cash Equivalents, at Carrying Value	$ 354,976	$ 720,861	$ 494,807	$ 593,000
Receivables	279,608	244,213
Inventory, Operative Builders	3,688,855	3,263,386
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	62,436	64,794
Deferred tax assets, net	468,969	633,637
Other assets	108,919	102,498
Investments in and Advances to Affiliates, Amount of Equity	0	0
Total assets	4,974,689	5,041,515
Due from Affiliates	0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities	894,413	789,393
Mortgages and notes payable	2,063,127	2,324,845
Financial services	1,200	966
Due to Affiliate	0	0
Stockholders' equity	2,015,949	1,926,311
Total liabilities and stockholders’ equity	4,974,689	5,041,515
KB Home Corporate
Assets
Cash and Cash Equivalents, at Carrying Value	245,197	575,193	400,956	463,100
Receivables	5,707	24,815
Inventory, Operative Builders	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Deferred tax assets, net	200,610	250,747
Other assets	97,542	91,592
Investments in and Advances to Affiliates, Amount of Equity	150,900	49,776
Total assets	4,184,575	4,406,360
Due from Affiliates	3,484,619	3,414,237
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities	137,171	163,984
Mortgages and notes payable	1,993,722	2,289,532
Financial services	0	0
Due to Affiliate	37,733	26,533
Stockholders' equity	2,015,949	1,926,311
Total liabilities and stockholders’ equity	4,184,575	4,406,360
Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value	86,201	102,661	82,622	100,439
Receivables	189,793	144,076
Inventory, Operative Builders	3,317,712	2,929,466
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	59,932	62,290
Deferred tax assets, net	155,451	243,523
Other assets	8,670	8,424
Investments in and Advances to Affiliates, Amount of Equity	0	0
Total assets	3,817,759	3,490,440
Due from Affiliates	0	0
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities	530,309	371,909
Mortgages and notes payable	44,295	9,283
Financial services	0	0
Due to Affiliate	3,152,077	3,109,248
Stockholders' equity	91,078	0
Total liabilities and stockholders’ equity	3,817,759	3,490,440
Non-Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value	23,578	43,007	11,229	29,461
Receivables	84,108	75,322
Inventory, Operative Builders	371,143	333,920
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	2,504	2,504
Deferred tax assets, net	112,908	139,367
Other assets	2,707	2,482
Investments in and Advances to Affiliates, Amount of Equity	0	0
Total assets	761,320	716,720
Due from Affiliates	153,446	107,992
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities	226,933	253,500
Mortgages and notes payable	25,110	26,030
Financial services	1,200	966
Due to Affiliate	448,255	386,448
Stockholders' equity	59,822	49,776
Total liabilities and stockholders’ equity	761,320	716,720
Homebuilding [Member]
Assets
Cash and Cash Equivalents, at Carrying Value	354,361	720,630	494,053
Total assets	4,963,148	5,029,158
Liabilities and stockholders' equity
Total Liabilities Homebuilding	2,957,540	3,114,238
Homebuilding [Member] | KB Home Corporate
Assets
Cash and Cash Equivalents, at Carrying Value	245,197	575,193
Total assets	549,056	942,347
Liabilities and stockholders' equity
Total Liabilities Homebuilding	2,130,893	2,453,516
Homebuilding [Member] | Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value	86,201	102,661
Total assets	3,817,759	3,490,440
Liabilities and stockholders' equity
Total Liabilities Homebuilding	574,604	381,192
Homebuilding [Member] | Non-Guarantor Subsidiaries
Assets
Cash and Cash Equivalents, at Carrying Value	22,963	42,776
Total assets	596,333	596,371
Liabilities and stockholders' equity
Total Liabilities Homebuilding	252,043	279,530
Financial services [Member]
Assets
Cash and Cash Equivalents, at Carrying Value	615	231	754
Receivables	2,358	1,724
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	8,408	10,340
Other assets	160	62
Total assets	11,541	12,357
Liabilities and stockholders' equity
Accounts payable, accrued expenses and other liabilities	1,200	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	11,541	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	(150,900)	(49,776)
Total assets	(3,788,965)	(3,572,005)
Due from Affiliates	(3,638,065)	(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	(3,638,065)	(3,522,229)
Stockholders' equity	(150,900)	(49,776)
Total liabilities and stockholders’ equity	(3,788,965)	(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