Debt (Narrative) (Details)	12 Months Ended
	Dec. 31, 2025 USD ($) Days $ / shares shares	Dec. 31, 2026 USD ($)	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 1,300,000,000
Long-term debt	12,125,000,000		$ 9,925,000,000
Current maturities of long-term debt	1,074,000,000		1,171,000,000
Long-term debt, fair value	$ 11,748,000,000		9,577,000,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Trading days | Days	20
Trading days consecutive | Days	30
3.875% senior notes, due 2026 [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 575,000,000
Interest rate, percent	3.875%
Trading days | Days	20
Trading days consecutive | Days	10
Principal amount of Notes conversion rate applied to	$ 1,000
Initial conversion ratio (in shares)	15.5461
Initial conversion price | $ / shares	$ 64.32
Fundamental change repurchase conversion price, percent	100.00%
Current maturities of long-term debt	$ 574,000,000
Long-term debt, carrying value			571,000,000
Unamortized debt issuance costs	1,000,000		4,000,000
Long-term debt, fair value	$ 599,000,000		591,000,000
Shares included in diluted earnings per share (in shares) | shares	407,821
Debt Instrument Convertible Threshold Business Days | Days	5
3.875% senior notes, due 2026 [Member] | Convertible Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Conversion price, percent	130.00%
Threshold, product of last report sale price of common stock and conversion rate	98.00%
3.875% senior notes, due 2026 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	$ 575,000,000		$ 575,000,000
Interest rate, percent	3.875%		3.875%
Trading days consecutive | Days	30
Three Point Two Five Percent Senior Notes Due Two Thousand Twenty Eight | Convertible Debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 575,000,000
Interest rate, percent	3.25%
Trading days | Days	5
Trading days consecutive | Days	10
Principal amount of Notes conversion rate applied to	$ 1,000
Initial conversion ratio (in shares)	13.1773
Initial conversion price | $ / shares	$ 75.89
Fundamental change repurchase conversion price, percent	100.00%
Long-term debt, carrying value	$ 569,000,000
Unamortized debt issuance costs	6,000,000
Long-term debt, fair value	$ 587,000,000
Three Point Two Five Percent Senior Notes Due Two Thousand Twenty Eight | Convertible Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Conversion price, percent	130.00%
Threshold, product of last report sale price of common stock and conversion rate	98.00%
Three Point Two Five Percent Senior Notes Due Two Thousand Twenty Eight | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	$ 575,000,000		$ 0
Interest rate, percent	3.25%
Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 550,000,000
Current maturities of long-term debt	574,000,000		571,000,000
IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	350,000,000
Long-term debt	4,725,000,000		4,125,000,000
Current maturities of long-term debt	0		300,000,000
Long-term debt, fair value	4,445,000,000		3,736,000,000
WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	400,000,000
Long-term debt	3,700,000,000		3,400,000,000
Current maturities of long-term debt	0		0
Long-term debt, fair value	$ 3,575,000,000		$ 3,170,000,000
Forecast [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 1,000,000,000
Forecast [Member] | IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		400,000,000
Forecast [Member] | WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 500,000,000