Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Nov. 03, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	CASTLE A M & CO
Entity Central Index Key	0000018172
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Amendment Flag	false
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		23,777,280