Document And Entity Information	3 Months Ended
	Mar. 31, 2012	May 03, 2011
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1
Entity Filer Category	Accelerated Filer
Entity Registrant Name	CSG SYSTEMS INTERNATIONAL INC
Entity Central Index Key	0001005757
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		33,978,977