Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 07, 2018
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Trading Symbol	WLH
Entity Registrant Name	WILLIAM LYON HOMES
Entity Central Index Key	0001095996
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Common stock, Class A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		33,202,209
Common stock, Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,817,394