Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 06, 2019
Software Development And Other Equipment In Progress [Member]
Entity Registrant Name	PCM, INC.
Entity Central Index Key	0000937941
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business Flag	true
Entity Emerging Growth Company	false
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		12,256,699
Trading Symbol	PCMI
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2019