Supplemental Guarantor Information (Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Feb. 28, 2018	Feb. 28, 2017
Cash flows from operating activities:
Net cash used in operating activities	$ (141,680)	$ (77,042)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(8,025)	(8,750)
Proceeds from Equity Method Investment, Distribution, Return of Capital	1,099	1,107
Purchases of property and equipment, net	(1,924)	(1,015)
Intercompany	0	0
Net cash used in investing activities	(8,850)	(8,658)
Cash flows from financing activities:
Repayment of senior notes		(105,326)
Payments on mortgages and land contracts due to land sellers and other loans	(3,362)	(45,428)
Issuance of common stock under employee stock plans	2,946	662
Payments of cash dividends	(2,322)	(2,215)
Stock repurchases	(6,787)	(2,543)
Intercompany	0	0
Net cash used in financing activities	(9,525)	(154,850)
Net decrease in cash and cash equivalents	(160,055)	(240,550)
Cash and cash equivalents at beginning of period	720,861	593,000
Cash and cash equivalents at end of period	560,806	352,450
KB Home Corporate
Cash flows from operating activities:
Net cash used in operating activities	3,066	11,773
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Proceeds from Equity Method Investment, Distribution, Return of Capital	0	0
Purchases of property and equipment, net	(1,776)	(892)
Intercompany	(114,691)	(106,903)
Net cash used in investing activities	(116,467)	(107,795)
Cash flows from financing activities:
Repayment of senior notes		(105,326)
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Issuance of common stock under employee stock plans	2,946	662
Payments of cash dividends	(2,322)	(2,215)
Stock repurchases	(6,787)	(2,543)
Intercompany	0	0
Net cash used in financing activities	(6,163)	(109,422)
Net decrease in cash and cash equivalents	(119,564)	(205,444)
Cash and cash equivalents at beginning of period	575,193	463,100
Cash and cash equivalents at end of period	455,629	257,656
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(134,364)	(71,130)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	(8,025)	(3,500)
Proceeds from Equity Method Investment, Distribution, Return of Capital	1,099	1,107
Purchases of property and equipment, net	(125)	(113)
Intercompany	0	0
Net cash used in investing activities	(7,051)	(2,506)
Cash flows from financing activities:
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	(2,442)	(45,428)
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	113,927	102,302
Net cash used in financing activities	111,485	56,874
Net decrease in cash and cash equivalents	(29,930)	(16,762)
Cash and cash equivalents at beginning of period	102,661	100,439
Cash and cash equivalents at end of period	72,731	83,677
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash used in operating activities	(10,382)	(17,685)
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	(5,250)
Proceeds from Equity Method Investment, Distribution, Return of Capital	0	0
Purchases of property and equipment, net	(23)	(10)
Intercompany	0	0
Net cash used in investing activities	(23)	(5,260)
Cash flows from financing activities:
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	(920)	0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	764	4,601
Net cash used in financing activities	(156)	4,601
Net decrease in cash and cash equivalents	(10,561)	(18,344)
Cash and cash equivalents at beginning of period	43,007	29,461
Cash and cash equivalents at end of period	32,446	11,117
Consolidating Adjustments
Cash flows from operating activities:
Net cash used in operating activities	0	0
Cash flows from investing activities:
Contributions to unconsolidated joint ventures	0	0
Proceeds from Equity Method Investment, Distribution, Return of Capital	0	0
Purchases of property and equipment, net	0	0
Intercompany	114,691	106,903
Net cash used in investing activities	114,691	106,903
Cash flows from financing activities:
Repayment of senior notes		0
Payments on mortgages and land contracts due to land sellers and other loans	0	0
Issuance of common stock under employee stock plans	0	0
Payments of cash dividends	0	0
Stock repurchases	0	0
Intercompany	(114,691)	(106,903)
Net cash used in financing activities	(114,691)	(106,903)
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0