Investments in joint ventures - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($)
BP Bunge Bioenergia [Member]
Disclosure of joint ventures [line items]
Proportion of ownership interest in joint venture	50.00%
Joint ventures
Disclosure of joint ventures [line items]
Provision for doubtful debts	$ 0
Doubtful debt provision, expense	$ 0
Joint ventures \| Minimum
Disclosure of joint ventures [line items]
Days sales outstanding, related party receivables	30 days
Joint ventures \| Maximum
Disclosure of joint ventures [line items]
Days sales outstanding, related party receivables	45 days

Amounts Receivable, Related Party Transactions,Days Sales Outstanding

No definition available.

Name:	bp_AmountsReceivableRelatedPartyTransactionsDaysSalesOutstanding
Namespace Prefix:	bp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfJointVenturesLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of expense recognised during the period in respect of bad or doubtful debts due from related parties. [Refer: Related parties [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2018-01-01
-Paragraph 18
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2018-03-01&anchor=para_18_d&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_ExpenseRecognisedDuringPeriodForBadAndDoubtfulDebtsForRelatedPartyTransaction
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The proportion of ownership interest in a joint venture attributable to the entity. [Refer: Joint ventures [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2018-01-01
-Paragraph 17
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2018-03-01&anchor=para_17_b_iii&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2018-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2018-03-01&anchor=para_16_b_iii&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph 21
-Subparagraph a
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_21_a_iv&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInJointVenture
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of provisions for doubtful debts related to the amount of outstanding balances in related party transactions. [Refer: Provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2018-01-01
-Paragraph 18
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2018-03-01&anchor=para_18_c&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_ProvisionsForDoubtfulDebtsRelatedToOutstandingBalancesOfRelatedPartyTransaction
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ifrs-full_JointVenturesAxis=bp_BPBungeBioenergiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointVenturesAxis=ifrs-full_JointVenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: