Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 30, 2019
Document Information [Line Items]
Entity Registrant Name	CBS Corporation
Entity Central Index Key	0000813828
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Small Business	false
Entity Emerging Growth Company	false
Common Class A [Member]
Document Information [Line Items]
Shares of common stock outstanding		22,858,062
Common Class B [Member]
Document Information [Line Items]
Shares of common stock outstanding		351,954,458