Financing: At-the-Market Equity Offering Program (Details) - Common Stock - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Proceeds, (net of issuance costs)	$ 154,300,000	$ 108,600,000	$ 219,600,000	$ 181,600,000
Average price per share	$ 59.47	$ 56.84	$ 59.56	$ 55.63
Number of shares issued	2,600,000	1,900,000	3,700,000	3,300,000
Payments of Stock Issuance Costs	$ (1,300,000)	$ (1,100,000)	$ (2,000,000)	$ (1,800,000)
June 16, 2023 ATM Program
Proceeds, (net of issuance costs)	$ 0	$ 108,600,000	$ 45,700,000	$ 181,600,000
Number of shares issued	0	1,900,000	800,000	3,300,000
Payments of Stock Issuance Costs	$ 0	$ (1,100,000)	$ (500,000)	$ (1,800,000)
May 8, 2025 ATM Program
Proceeds, (net of issuance costs)	$ 154,300,000	$ 0	$ 173,900,000	$ 0
Number of shares issued	2,600,000	0	2,900,000	0
Payments of Stock Issuance Costs	$ (1,300,000)	$ 0	$ (1,500,000)	$ 0