Debt (Schedule of Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Commercial paper	$ 0	$ 699
Other bank borrowings	101	0
Obligations under finance leases	37	44
Total debt	20,068	18,719
Less commercial paper and other short-term borrowings	6	699
Less current portion of long-term debt	358	18
Total long-term debt, net of current portion	19,704	18,002
Net unamortized discount on senior debt	503	412
Unamortized deferred financing costs	112	92
Decrease (increase) in the carrying value of debt relating to previously settled fair value hedges	5	6
Face value of debt	20,690	19,230
4.30% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 0	300
Stated interest rate	4.30%
4.50% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 0	499
Stated interest rate	4.50%
3.875% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 339	597
Stated interest rate	3.875%
2.250% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 35	49
Stated interest rate	2.25%
3.375% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 415	698
Stated interest rate	3.375%
3.125% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 117	194
Stated interest rate	3.125%
2.50% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 196	398
Stated interest rate	2.50%
3.25% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 141	181
Stated interest rate	3.25%
2.90% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 242	396
Stated interest rate	2.90%
4.25% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 836	1,242
Stated interest rate	4.25%
7.875% Debentures due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 139	187
Stated interest rate	7.875%
7.125% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 35	46
Stated interest rate	7.125%
3.875% Senior Notes due 2024 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 490	489
Stated interest rate	3.875%
3.70% Senior Notes due 2024 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 598	598
Stated interest rate	3.70%
3.50% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 593	592
Stated interest rate	3.50%
4.75% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 1,238	0
Stated interest rate	4.75%
4.00% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 790	789
Stated interest rate	4.00%
3.45% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 123	123
Stated interest rate	3.45%
2.90% Senior Notes due 2027 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 689	688
Stated interest rate	2.90%
3.375% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 494	494
Stated interest rate	3.375%
3.70% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 491	491
Stated interest rate	3.70%
4.20% Senior Notes due 2029 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 493	493
Stated interest rate	4.20%
7.875% Senior Debentures due 2030 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 831	831
Stated interest rate	7.875%
4.95% Senior Notes due 2031 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 1,218	0
Stated interest rate	4.95%
4.20% Senior Notes due 2032 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 968	0
Stated interest rate	4.20%
5.50% Senior Debentures due 2033 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 426	426
Stated interest rate	5.50%
4.85% Senior Debentures due 2034 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 87	87
Stated interest rate	4.85%
6.875% Senior Debentures due 2036 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 1,069	1,068
Stated interest rate	6.875%
6.75% Senior Debentures due 2037 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 75	75
Stated interest rate	6.75%
5.90% Senior Notes due 2040 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 298	297
Stated interest rate	5.90%
4.50% Senior Debentures due 2042 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 45	45
Stated interest rate	4.50%
4.85% Senior Notes due 2042 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 487	486
Stated interest rate	4.85%
4.375% Senior Debentures due 2043 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 1,112	1,109
Stated interest rate	4.375%
4.875% Senior Debentures due 2043 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 18	18
Stated interest rate	4.875%
5.850% Senior Debentures due 2043 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 1,231	1,231
Stated interest rate	5.85%
5.25% Senior Debentures due 2044 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 345	345
Stated interest rate	5.25%
4.90% Senior Notes due 2044 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 539	539
Stated interest rate	4.90%
4.60% Senior Notes due 2045 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 589	589
Stated interest rate	4.60%
4.95% Senior Notes due 2050 [Member]
Debt Instrument [Line Items]
Carrying value of senior debt	$ 941	0
Stated interest rate	4.95%
5.875% Junior Subordinated Debentures due 2057 [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes	$ 514	643
Stated interest rate	5.875%
6.25% Junior Subordinated Debentures due 2057 [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes	$ 643	$ 643
Stated interest rate	6.25%

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(2))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a)(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommercialPaper
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of short-term and long-term debt and lease obligation.

+ References

+ Details

Name:	us-gaap_DebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount (premium).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28567-108399

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount as of the balance sheet date of the unamortized adjustment to the carrying value of an interest-bearing hedged item made under an effective fair value hedge that is amortized upon discontinuation of the fair value hedge.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 35
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121561968&loc=d3e75592-113984

+ Details

Name:	us-gaap_DeferredGainLossOnDiscontinuationOfFairValueHedge
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977

+ Details

Name:	us-gaap_FinanceLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16)(a))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_JuniorSubordinatedNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt and lease obligation, classified as noncurrent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt and lease obligation, classified as current.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, the carrying value as of the balance sheet date of notes payable to banks, excluding mortgage notes, initially due beyond one year or beyond the operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_NotesPayableToBank
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Commercial Paper And Short Term Debt

+ References

No definition available.

+ Details

Name:	viac_CommercialPaperAndShortTermDebt
Namespace Prefix:	viac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant