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, 2020		226,836,670
Beginning balance at Dec. 31, 2020	$ 8,718.5	$ 7,080.0	$ 1,702.8	$ (49.4)	$ (14.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	891.9		879.7		12.2
Issuance of stock, net of issuance costs (in shares)		2,269,447
Issuance of stock, net of issuance costs	112.5	$ 112.5
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		139,729
Issuance of stock, net issuance costs	(2.4)	$ (2.4)
Issuance of restricted common stock (in shares)		54,054
Issuance of restricted common stock	2.9	$ 2.9
Dividends declared on common stock	(497.9)		(497.9)
Dividend equivalents declared	(1.7)		(1.7)
Stock compensation expense	13.8	13.8
Unearned compensation
Issuance of restricted common stock	(2.9)	(2.9)
Compensation expense recognized	1.8	1.8
Derivative hedging activity, net of tax	5.5			5.5
Change in unrecognized pension expense, net of tax	(0.1)			(0.1)
Other	(0.2)	$ (0.2)
Ending balance (in shares) at Dec. 31, 2021		229,299,900
Ending balance at Dec. 31, 2021	9,241.7	$ 7,205.5	2,082.9	(44.0)	(2.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	765.0		752.7		12.3
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		246,205
Issuance of stock, net issuance costs	(5.2)	$ (5.2)
Dividends declared on common stock	(534.8)		(534.8)
Dividend equivalents declared	(2.3)		(2.3)
Stock compensation expense	18.1	18.1
Unearned compensation
Compensation expense recognized	0.7	0.7
Derivative hedging activity, net of tax	5.5			5.5
Change in unrecognized pension expense, net of tax	4.0			4.0
Other	0.6	$ 0.6
Ending balance (in shares) at Dec. 31, 2022		229,546,105
Ending 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	743.6		731.3		12.3
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		183,191
Issuance of stock, net issuance costs	(2.5)	$ (2.5)
Dividends declared on common stock	(569.6)		(569.6)
Dividend equivalents declared	(2.4)		(2.4)
Stock compensation expense	17.5	17.5
Unearned compensation
Compensation expense recognized	0.2	$ 0.2
Derivative hedging activity, net of tax	5.4			5.4
Change in unrecognized pension expense, net of tax	(0.5)			(0.5)
Ending balance (in shares) at Dec. 31, 2023		229,729,296
Ending balance at Dec. 31, 2023	$ 9,685.0	$ 7,234.9	$ 2,457.8	$ (29.6)	$ 21.9