Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011	Feb. 29, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
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		34,515,397
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 639,546,766