Leases - Lessee (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Lease, Cost [Abstract]
Operating leases	$ 136
Short-term and variable leases	92
Total lease cost(a)	228
Lease Costs Capitalized	46
Lessee, Operating Lease, Description [Abstract]
Operating cash flows from operating leases	(182)
Investing cash flows from operating leases	(46)
ROU assets obtained in exchange for operating lease obligations, net of retirements adjusted for currency conversion	399
Amortization of ROU assets	$ 75
Weighted average remaining lease term	13 years 4 months 24 days
Weighted average discount rate	4.31%
Assets and Liabilities, Lessee [Abstract]
ROU assets	$ 329
Short-term lease liability	40
Long-term lease liability	289
Finance lease assets	2
Finance lease liabilities	2
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020	55
2021	45
2022	38
2023	32
2024	30
Thereafter	267
Total lease payments	467
Less: Interest	(138)
Present value of lease liabilities	329
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019			$ 115
2020			100
2021			95
2022			91
2023			84
Thereafter			859
Total payments			1,344
Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019			90
2020			75
2021			70
2022			65
2023			59
Thereafter			771
Total payments			1,130
ROW
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Total lease payments	202
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019			25
2020			25
2021			25
2022			26
2023			25
Thereafter			88
Total payments			214
Edmonton South Property
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Total payments			482
KML and U.S. Portion of Cochin Pipeline
Lessee, Operating Lease, Description [Abstract]
Removal of ROU assets and liabilities associated with the KML and U.S. Cochin Sale	(394)
KML and U.S. Portion of Cochin Pipeline | Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Total payments			$ 695
Amount Excluding Cumulative Adjustment
Lessee, Operating Lease, Description [Abstract]
ROU assets obtained in exchange for operating lease obligations, net of retirements adjusted for currency conversion	$ 102
Accounting Standards Update 2016-02
Assets and Liabilities, Lessee [Abstract]
ROU assets		$ 696
Short-term lease liability		52
Long-term lease liability		$ 644