Common Equity Narrative (Details) - USD ($) $ / shares in Units, $ in Millions							1 Months Ended							2 Months Ended	12 Months Ended
	Dec. 29, 2023	Dec. 05, 2023	Nov. 30, 2023	Nov. 21, 2023	Jun. 28, 2023	Jun. 06, 2023	Nov. 30, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Oct. 31, 2021	Aug. 31, 2021	Jun. 30, 2021	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	May 31, 2022	Oct. 31, 2010
Common Stock, Dividends, Per Share, Declared															$ 4.34	$ 4.10	$ 3.86
Proceeds from Dividends Received															$ 189.0	$ 301.0	$ 136.0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount															1,179,962	931,453	1,013,320
Stock Repurchase Program, Authorized Amount																			$ 500.0
Stock Repurchase Program, Remaining Authorized Repurchase Amount														$ 350.0	$ 350.0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount															1,179,962	931,453	1,013,320
Equity Distribution Program [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount															1,762,709	1,158,917	1,158,917
Forward Contract Indexed to Equity, Settlement, Cash, Amount																$ 1,500.0
Equity Distribution Sales Agreement Increase in Aggregate Gross Sales Price																		$ 2,000.0
Forward Sale Agreement, Aggregate Compensation to Forward Sellers	$ 2.8			$ 0.8	$ 0.4	$ 0.1		$ 1.9	$ 2.5	$ 1.7	$ 0.3	$ 1.9	$ 0.5
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount															1,762,709	1,158,917	1,158,917
Equity Distribution Program [Member] | Common Stock [Member]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share	$ 101.11	$ 97.48	$ 101.38	$ 97.48	$ 101.39	$ 101.36	$ 112.50	$ 115.46	$ 116.94	$ 108.12	$ 100.35	$ 111.16	$ 106.87
Forward Contract Indexed to Equity, Settlement, Cash, Amount	$ 280.5	$ 83.3	$ 47.8	$ 84.0	$ 37.4	$ 10.5	$ 853.3	$ 194.2	$ 250.9	$ 168.0	$ 25.4	$ 190.1	$ 45.0
Forward Contract Indexed to Issuer's Equity, Indexed Shares	2,753,246			853,117	365,307	102,995		1,666,172	2,124,086	1,538,010	250,743	1,692,555	416,853
Forward Contract Indexed to Equity, Settlement, Number of Shares		853,117	468,302	853,117	365,307	102,995	7,688,419	1,666,172	2,124,086	1,538,010	250,743	1,692,555	416,853
General Issuance Costs							$ 0.7							0.4			$ 1.4
Net Sales Proceeds																	200.8
Gross Sales Price																	204.2
Aggregate Compensation to Sales Agents																	$ 2.0
Stock Issued During Period, Shares, New Issues															0	0	1,930,330
Stock Issued During Period, Shares, New Issues															0	0	1,930,330
Net Sales Proceeds																	$ 200.8
Gross Sales Price																	204.2
General Issuance Costs							$ 0.7							$ 0.4			1.4
Aggregate Compensation to Sales Agents																	$ 2.0
Common Stock [Member]
Stock Issued During Period, Shares, New Issues															1,321,419	7,688,419	1,930,330
Stock Issued During Period, Shares, New Issues															1,321,419	7,688,419	1,930,330