Debt (Commercial Paper Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jan. 31, 2020
Line of Credit Facility [Line Items]
Commercial paper	$ 312,000,000	$ 699,000,000
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity under credit facility		$ 2,500,000,000	$ 3,500,000,000
Debt maturity, less than	90 days	90 days
Weighted average interest rate	2.18%	2.07%
ViacomCBS Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity under credit facility			$ 3,500,000,000