Financial and Other Derivative Instruments (Netting Offsets of Derivative Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Derivative assets
Gross Amounts of Recognized Assets (Liabilities)	$ 707	$ 694
Gross Amounts Offset in the Consolidated Statements of Financial Position	(475)	(447)
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	232	247
Derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(597)	(605)
Gross Amounts Offset in the Consolidated Statements of Financial Position	445	430
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	(152)	(175)
Natural gas
Derivative assets
Gross Amounts of Recognized Assets (Liabilities)	372	428
Gross Amounts Offset in the Consolidated Statements of Financial Position	(235)	(285)
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	137	143
Derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(329)	(410)
Gross Amounts Offset in the Consolidated Statements of Financial Position	227	272
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	(102)	(138)
Electricity
Derivative assets
Gross Amounts of Recognized Assets (Liabilities)	275	187
Gross Amounts Offset in the Consolidated Statements of Financial Position	(194)	(116)
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	81	71
Derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(235)	(150)
Gross Amounts Offset in the Consolidated Statements of Financial Position	186	114
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	(49)	(36)
Environmental & Other
Derivative assets
Gross Amounts of Recognized Assets (Liabilities)	57	58
Gross Amounts Offset in the Consolidated Statements of Financial Position	(46)	(46)
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	11	12
Derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(32)	(44)
Gross Amounts Offset in the Consolidated Statements of Financial Position	32	44
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	0	0
Interest rate contracts (Enter as Other)
Derivative assets
Gross Amounts of Recognized Assets (Liabilities)	3	20
Gross Amounts Offset in the Consolidated Statements of Financial Position	0	0
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	3	20
Foreign currency exchange contracts
Derivative assets
Gross Amounts of Recognized Assets (Liabilities)	0	1
Gross Amounts Offset in the Consolidated Statements of Financial Position	0	0
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	0	1
Derivative liabilities
Gross Amounts of Recognized Assets (Liabilities)	(1)	(1)
Gross Amounts Offset in the Consolidated Statements of Financial Position	0	0
Net Amounts of Assets (Liabilities) Presented in the Consolidated Statements of Financial Position	$ (1)	$ (1)