Short-term Borrowings and Long-term Debt (Schedule of Long-term Debt Instruments) (Details) - USD ($) $ in Millions	6 Months Ended
Jan. 26, 2020	Jul. 28, 2019
Debt Instrument [Line Items]
Finance Lease, Liability, Noncurrent	$ 4	$ 3
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(35)	(49)
Long-term Debt and Lease Obligation, Including Current Maturities	5,419	7,603
Long-term Debt, Current Maturities	500	500
Long-term debt	$ 4,919	7,103
Variable Interest Rate due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	Variable
Long-term Debt, Gross	$ 500	500
Debt Instrument, Maturity Date	Mar. 16, 2020
Variable Interest Rate due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	Variable
Long-term Debt, Gross	$ 400	400
Debt Instrument, Maturity Date	Mar. 15, 2021
Variable Interest Rate Term Loan due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	Variable
Long-term Debt, Gross	$ 0	499
Debt Instrument, Maturity Date	Mar. 26, 2021
3.3% notes, due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Long-term Debt, Gross	$ 321	650
Debt Instrument, Maturity Date	Mar. 15, 2021
4.25% notes, due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Long-term Debt, Gross	$ 0	500
Debt Instrument, Maturity Date	Apr. 15, 2021
8.88% notes, due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.88%
Long-term Debt, Gross	$ 200	200
Debt Instrument, Maturity Date	May 01, 2021
2.50% notes, due 2023
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.50%
Long-term Debt, Gross	$ 450	450
Debt Instrument, Maturity Date	Aug. 02, 2022
3.65% notes, due 2023
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.65%
Long-term Debt, Gross	$ 566	1,200
Debt Instrument, Maturity Date	Mar. 15, 2023
3.95% notes, due 2025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Long-term Debt, Gross	$ 850	850
Debt Instrument, Maturity Date	Mar. 15, 2025
3.30% notes, due 2025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Long-term Debt, Gross	$ 300	300
Debt Instrument, Maturity Date	Mar. 19, 2025
4.15% notes, due 2028
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.15%
Long-term Debt, Gross	$ 1,000	1,000
Debt Instrument, Maturity Date	Mar. 15, 2028
3.80% notes, due 2042
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.80%
Long-term Debt, Gross	$ 163	400
Debt Instrument, Maturity Date	Aug. 02, 2042
4.80% notes, due 2048
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.80%
Long-term Debt, Gross	$ 700	$ 700
Debt Instrument, Maturity Date	Mar. 15, 2048

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

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(16))
-URI http://asc.fasb.org/extlink&oid=119400593&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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: 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=6876686&loc=d3e534808-122878

+ Details

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

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- 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=6877327&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

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet
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, classified as noncurrent.

+ References

Reference 1: 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=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_FinanceLeaseLiabilityNoncurrent
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=6877327&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, including portion classified as current.

+ References

No definition available.

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ 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 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_VariableInterestRatedue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_VariableInterestRatedue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_VariableInterestRateTermLoandue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_ThreePointThreeZeroPercentNotesMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_FourPointTwentyFivePercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_EightPointEightyEightPercentDebenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_TwoPointFivePercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_ThreePointSixFivePercentNotesMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_ThreePointNineFivePercentNotesMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_ThreePointThreeZeroPercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_FourPointOneFivePercentNotesMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_ThreePointEightZeroPercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cpb_FourPointEightZeroPercentNotesMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: