Leases - Operating lease reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of future undiscounted cash flows to the operating lease liabilities and the related ROU assets
2021	$ 51
2022	43
2023	33
2024	23
2025	15
Thereafter	37
Total future lease payments	202
Less imputed interest	20
Present value of future lease payments	$ 182
Operating Lease, Liability, Statement of Financial Position	us-gaap:AccruedLiabilitiesCurrent us-gaap:OperatingLeaseLiabilityNoncurrent	us-gaap:AccruedLiabilitiesCurrent us-gaap:OperatingLeaseLiabilityNoncurrent	us-gaap:AccruedLiabilitiesCurrent us-gaap:OperatingLeaseLiabilityNoncurrent
Less current lease liabilities	$ 46	$ 41
Operating Lease, Liability, Current, Statement of Financial Position	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Non-current operating lease liabilities	$ 136	$ 120
Operating lease assets	$ 173	$ 151
ASU 2016-02, Leases \| Cumulative Effect, Period of Adoption, Adjustment
Reconciliation of future undiscounted cash flows to the operating lease liabilities and the related ROU assets
Present value of future lease payments			$ 170
Operating lease assets			$ 161

Amount of lessee's undiscounted obligation for lease payment for operating lease.

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

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Amount of lessee's undiscounted obligation for lease payment for operating lease due after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

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

+ 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=121603541&loc=SL77918627-209977

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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Indicates line item in statement of financial position that includes current operating lease liability.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918631-209977

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

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Indicates line item in statement of financial position that includes operating lease liability.

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Amount of lessee's right to use underlying asset under operating lease.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977

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