Segment and Revenue Information (Operating Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Stock-based compensation									$ (274)	$ (286)	$ (187)
Depreciation and amortization									(430)	(438)	(427)
Restructuring and other corporate matters	$ (177)	$ (52)	$ (158)	$ (231)	$ (467)	$ (122)	$ (7)	$ (173)	(618)	(769)	(489)
Programming charges	(38)		(121)		(589)				(159)	(589)	(162)
Gain on sales									214	549	0
Operating income (loss)	1,083	903	1,251	902	(44)	984	1,414	1,792	4,139	4,146	5,062
Interest expense									(1,031)	(962)	(1,030)
Interest income									60	66	79
Net gains (losses) from investments									206	85	(53)
Gain (loss) on extinguishment of debt		(23)	(103)						(126)	0	18
Other items, net									(101)	(112)	(92)
Earnings from continuing operations before income taxes and equity in loss of investee companies									3,147	3,223	3,984
(Provision) benefit for income taxes									(535)	29	(580)
Equity in loss of investee companies, net of tax									(28)	(53)	(47)
Net earnings from continuing operations	802	580	698	504	(298)	600	953	1,944	2,584	3,199	3,357
Net earnings from discontinued operations, net of tax									117	140	135
Net earnings (ViacomCBS and noncontrolling interests)	829	627	726	519	(254)	646	983	1,964	2,701	3,339	3,492
Net earnings attributable to noncontrolling interests									(279)	(31)	(37)
Net earnings attributable to ViacomCBS	$ 810	$ 615	$ 481	$ 516	$ (258)	$ 630	$ 977	$ 1,959	2,422	3,308	3,455
TV Entertainment [Member]
Segment Reporting Information [Line Items]
Programming charges									(101)
Cable Networks [Member]
Segment Reporting Information [Line Items]
Programming charges									(53)
Filmed Entertainment [Member]
Segment Reporting Information [Line Items]
Programming charges									(5)
Operating Segments [Member] | TV Entertainment [Member]
Segment Reporting Information [Line Items]
Adjusted OIBDA									1,857	2,443	2,466
Depreciation and amortization									(162)	(150)	(160)
Operating Segments [Member] | Cable Networks [Member]
Segment Reporting Information [Line Items]
Adjusted OIBDA									3,746	3,515	4,341
Depreciation and amortization									(205)	(219)	(194)
Operating Segments [Member] | Filmed Entertainment [Member]
Segment Reporting Information [Line Items]
Adjusted OIBDA									215	80	(33)
Depreciation and amortization									(36)	(37)	(38)
Corporate [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization									(27)	(32)	(35)
Corporate/Eliminations [Member]
Segment Reporting Information [Line Items]
Adjusted OIBDA									(500)	(449)	(433)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Stock-based compensation									(186)	(196)	(201)
Depreciation and amortization									(430)	(438)	(427)
Restructuring and other corporate matters									(618)	(769)	(489)
Programming charges									$ (159)	$ (589)	$ (162)