Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	Apr. 28, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	CBS Corporation
Entity Central Index Key	0000813828
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Common Class A [Member]
Shares of common stock outstanding		37,598,604
Common Class B [Member]
Shares of common stock outstanding		368,358,084