Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 31, 2017
Document Information [Line Items]
Entity Registrant Name	CBS Corporation
Entity Central Index Key	0000813828
Document Type	10-Q
Document Period End Date	Jun. 30, 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	Q2
Common Class A [Member]
Document Information [Line Items]
Shares of common stock outstanding		37,598,604
Common Class B [Member]
Document Information [Line Items]
Shares of common stock outstanding		364,054,978