Postretirement Benefits (Details) (USD $)	12 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2009
Postretirement Benefits Additional (Textual) [Abstract]
Net Periodic benefit cost	$ 5,500,000	$ 5,500,000	$ 5,600,000
Service cost	1,200,000	1,200,000	1,100,000
Interest cost	2,300,000	2,200,000	2,400,000
Amortization of unrecognized loss cost	600,000	300,000	0
Plan settlement cost			800,000
Other income that partly offset net periodic benefit cost	100,000		200,000
Amortization of prior service cost	1,500,000	1,600,000	1,500,000
Other cost	0	200,000
Liabilities related to postretirement benefit plan	53,100,000	44,100,000
Discounted rate for benefit plan	4.40%	5.20%
Defined Benefit Plan Disclosure [Line Items]
Cash surrender value of insurance contracts	59,718,000	59,103,000
2012	300,000
2013	1,000,000
2014	1,500,000
2015	1,600,000
2016	2,400,000
2017 - 2021	16,600,000
Supplemental Nonqualified Unfunded Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash surrender value of insurance contracts under KB Home Retirement Plan	41,700,000	41,400,000
Unfunded Death Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash surrender value of insurance contracts	13,700,000	13,600,000
Kb Home Retirement Plan and Kb Home Supplemental Executive Officer Under Kb Home Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement of certain stockholder derivative litigation			$ 22,200,000