Revenues from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Product and service revenues	$ 8,663	$ 8,943	$ 10,661
Sales of Purchased Product [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,487	1,585	2,849
Sales of Purchased Product [Member] \| Market Optimization Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,487	1,585	2,849
Operating Segments [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	5,884	7,061	8,176
Operating Segments [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	2,779	1,882	2,485
Operating Segments [Member] \| Sales of Purchased Product [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,311	1,449	2,590
Operating Segments [Member] \| Sales of Purchased Product [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	176	136	259
Corporate & Other [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0	0
Corporate & Other [Member] \| Sales of Purchased Product [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	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	0	0	0
Oil [Member] \| Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	3,423	4,559	4,447
Oil [Member] \| Operating Segments [Member] \| Product Revenue [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	3,413	4,549	4,444
Oil [Member] \| Operating Segments [Member] \| Product Revenue [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	10	10	3
Oil [Member] \| Corporate & Other [Member] \| Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0	0
Natural Gas Liquids [Member] \| Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	2,115	1,732	1,708
Natural Gas Liquids [Member] \| Operating Segments [Member] \| Product Revenue [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	693	740	679
Natural Gas Liquids [Member] \| Operating Segments [Member] \| Product Revenue [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,422	992	1,029
Natural Gas Liquids [Member] \| Corporate & Other [Member] \| Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0	0
Natural Gas [Member] \| Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,606	1,059	1,650
Natural Gas [Member] \| Operating Segments [Member] \| Product Revenue [Member] \| USA Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	447	318	458
Natural Gas [Member] \| Operating Segments [Member] \| Product Revenue [Member] \| Canadian Operations Excluding Intercompany Segment Transactions [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	1,159	741	1,192
Natural Gas [Member] \| Corporate & Other [Member] \| Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	0	0	0
Natural Gas Gathering and Processing, and Other [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	32	8	7
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	20	5	5
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	12	3	2
Natural Gas Gathering and Processing, and Other [Member] \| Corporate & Other [Member]
Disaggregation of Revenue [Line Items]
Product and service revenues	$ 0	$ 0	$ 0