Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Common Stock	Retained earnings	AOCI	Non-controlling interests
Beginning balance (in shares) at Dec. 31, 2022		229,546,105
Beginning balance at Dec. 31, 2022	$ 9,493.3	$ 7,219.7	$ 2,298.5	$ (34.5)	$ 9.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	145.7		142.6		3.1
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		130,594
Issuance of stock, net issuance costs	(2.4)	$ (2.4)
Dividends declared on common stock	(140.7)		(140.7)
Dividend equivalents declared	(0.4)		(0.4)
Stock compensation expense	4.7	4.7
Unearned compensation
Compensation expense recognized	0.1	0.1
Derivative hedging activity, net of tax	1.3			1.3
Other	0.1	$ 0.1
Ending balance (in shares) at Mar. 31, 2023		229,676,699
Ending balance at Mar. 31, 2023	9,501.7	$ 7,222.2	2,300.0	(33.2)	12.7
Beginning balance (in shares) at Dec. 31, 2022		229,546,105
Beginning balance at Dec. 31, 2022	9,493.3	$ 7,219.7	2,298.5	(34.5)	9.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	682.5
Unearned compensation
Derivative hedging activity, net of tax	4.1
Change in unrecognized pension expense, net of tax	(0.1)
Ending balance (in shares) at Sep. 30, 2023		229,716,510
Ending balance at Sep. 30, 2023	9,767.8	$ 7,231.5	2,548.0	(30.5)	18.8
Beginning balance (in shares) at Mar. 31, 2023		229,676,699
Beginning balance at Mar. 31, 2023	9,501.7	$ 7,222.2	2,300.0	(33.2)	12.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	182.2		179.1		3.1
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		25,010
Issuance of stock, net issuance costs	0.0	$ 0.0
Dividends declared on common stock	(140.7)		(140.7)
Dividend equivalents declared	(0.6)		(0.6)
Stock compensation expense	6.6	6.6
Unearned compensation
Compensation expense recognized	0.1	0.1
Derivative hedging activity, net of tax	1.3			1.3
Other	0.1	$ 0.1
Ending balance (in shares) at Jun. 30, 2023		229,701,709
Ending balance at Jun. 30, 2023	9,550.7	$ 7,229.0	2,337.8	(31.9)	15.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	354.6		351.6		3.0
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		14,801
Issuance of stock, net issuance costs	(0.1)	$ (0.1)
Dividends declared on common stock	(140.6)		(140.6)
Dividend equivalents declared	(0.8)		(0.8)
Stock compensation expense	2.5	2.5
Unearned compensation
Derivative hedging activity, net of tax	1.5			1.5
Change in unrecognized pension expense, net of tax	(0.1)			(0.1)
Other	0.1	$ 0.1
Ending balance (in shares) at Sep. 30, 2023		229,716,510
Ending balance at Sep. 30, 2023	9,767.8	$ 7,231.5	2,548.0	(30.5)	18.8
Beginning balance (in shares) at Dec. 31, 2023		229,729,296
Beginning balance at Dec. 31, 2023	9,685.0	$ 7,234.9	2,457.8	(29.6)	21.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	125.8		122.7		3.1
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		193,042
Issuance of stock, net issuance costs	(4.0)	$ (4.0)
Dividends declared on common stock	(147.7)		(147.7)
Dividend equivalents declared	(0.4)		(0.4)
Stock compensation expense	3.9	3.9
Unearned compensation
Derivative hedging activity, net of tax	1.3			1.3
Other	0.2	$ 0.2
Ending balance (in shares) at Mar. 31, 2024		229,922,338
Ending balance at Mar. 31, 2024	9,664.1	$ 7,235.0	2,432.4	(28.3)	25.0
Beginning balance (in shares) at Dec. 31, 2023		229,729,296
Beginning balance at Dec. 31, 2023	9,685.0	$ 7,234.9	2,457.8	(29.6)	21.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	804.5
Unearned compensation
Derivative hedging activity, net of tax	4.1
Change in unrecognized pension expense, net of tax	(0.1)
Ending balance (in shares) at Sep. 30, 2024		229,972,832
Ending balance at Sep. 30, 2024	10,056.2	$ 7,242.4	2,808.3	(25.6)	31.1
Beginning balance (in shares) at Mar. 31, 2024		229,922,338
Beginning balance at Mar. 31, 2024	9,664.1	$ 7,235.0	2,432.4	(28.3)	25.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	210.1		207.0		3.1
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		32,186
Issuance of stock, net issuance costs	(0.1)	$ (0.1)
Dividends declared on common stock	(147.7)		(147.7)
Dividend equivalents declared	(0.4)		(0.4)
Stock compensation expense	4.2	4.2
Unearned compensation
Derivative hedging activity, net of tax	1.4			1.4
Other	0.1	$ 0.1
Ending balance (in shares) at Jun. 30, 2024		229,954,524
Ending balance at Jun. 30, 2024	9,731.7	$ 7,239.2	2,491.3	(26.9)	28.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	468.6		465.6		3.0
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		18,308
Issuance of stock, net issuance costs	(0.4)	$ (0.4)
Dividends declared on common stock	(147.8)		(147.8)
Dividend equivalents declared	(0.8)		(0.8)
Stock compensation expense	3.4	3.4
Unearned compensation
Derivative hedging activity, net of tax	1.4			1.4
Change in unrecognized pension expense, net of tax	(0.1)			(0.1)
Other	0.2	$ 0.2
Ending balance (in shares) at Sep. 30, 2024		229,972,832
Ending balance at Sep. 30, 2024	$ 10,056.2	$ 7,242.4	$ 2,808.3	$ (25.6)	$ 31.1