Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Jul. 25, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	CBS Corporation
Entity Central Index Key	0000813828
Document Type	10-Q
Document Period End Date	Jun. 30, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Common Class A [Member]
Shares of common stock outstanding		37,726,904
Common Class B [Member]
Shares of common stock outstanding		406,874,849