Revenues from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Product and service revenues	$ 2,577	$ 2,375
Sales of Purchased Product [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	356	410
Sales of Purchased Product [Member] \| Market Optimization Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	89	42
Operating Segments [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,496	1,680
Operating Segments [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,081	695
Operating Segments [Member] \| Sales of Purchased Product [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0
Operating Segments [Member] \| Sales of Purchased Product [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	356	410
Corporate & Other [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0
Corporate & Other [Member] \| Sales of Purchased Product [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0
Corporate & Other [Member] \| Sales of Purchased Product [Member] \| Market Optimization Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	267	368
Oil [Member] \| Product Revenues [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	928	977
Oil [Member] \| Operating Segments [Member] \| Product Revenues [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	923	975
Oil [Member] \| Operating Segments [Member] \| Product Revenues [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	5	2
Oil [Member] \| Corporate & Other [Member] \| Product Revenues [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0
Natural Gas Liquids [Member] \| Product Revenues [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	685	513
Natural Gas Liquids [Member] \| Operating Segments [Member] \| Product Revenues [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	162	190
Natural Gas Liquids [Member] \| Operating Segments [Member] \| Product Revenues [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	523	323
Natural Gas Liquids [Member] \| Corporate & Other [Member] \| Product Revenues [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0
Natural Gas [Member] \| Product Revenues [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	601	472
Natural Gas [Member] \| Operating Segments [Member] \| Product Revenues [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	141	145
Natural Gas [Member] \| Operating Segments [Member] \| Product Revenues [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	460	327
Natural Gas [Member] \| Corporate & Other [Member] \| Product Revenues [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0
Natural Gas Gathering and Processing, and Other [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	7	3
Natural Gas Gathering and Processing, and Other [Member] \| Operating Segments [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	3	2
Natural Gas Gathering and Processing, and Other [Member] \| Operating Segments [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	4	1
Natural Gas Gathering and Processing, and Other [Member] \| Corporate & Other [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	$ 0	$ 0