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, 2021		229,299,900
Beginning 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	125.6		122.5		3.1
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		176,658
Issuance of stock, net issuance costs	(4.0)	$ (4.0)
Dividends declared on common stock	(131.3)		(131.3)
Issuance of restricted common stock	(0.8)		(0.8)
Stock compensation expense	4.3	4.3
Unearned compensation
Compensation expense recognized	0.2	0.2
Issuance of restricted common stock	1.4			1.4
Other	0.4	$ 0.4
Ending balance (in shares) at Mar. 31, 2022		229,476,558
Ending balance at Mar. 31, 2022	9,237.5	$ 7,206.4	2,073.3	(42.6)	0.4
Beginning balance (in shares) at Dec. 31, 2021		229,299,900
Beginning 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	323.2
Unearned compensation
Issuance of restricted common stock	2.7
Compensation expense recognized	0.1
Ending balance (in shares) at Jun. 30, 2022		229,515,301
Ending balance at Jun. 30, 2022	9,310.8	$ 7,212.5	2,136.0	(41.2)	3.5
Beginning balance (in shares) at Mar. 31, 2022		229,476,558
Beginning balance at Mar. 31, 2022	9,237.5	$ 7,206.4	2,073.3	(42.6)	0.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	197.6		194.5		3.1
Issuance of stock compensation and reinvested dividends, net of tax withholding (in shares)		38,743
Issuance of stock, net issuance costs	(0.3)	$ (0.3)
Dividends declared on common stock	(131.4)		(131.4)
Issuance of restricted common stock	(0.4)		(0.4)
Stock compensation expense	6.3	6.3
Unearned compensation
Compensation expense recognized	0.2	0.2
Issuance of restricted common stock	1.3			1.3
Compensation expense recognized	0.1			0.1
Other	(0.1)	$ (0.1)
Ending balance (in shares) at Jun. 30, 2022		229,515,301
Ending balance at Jun. 30, 2022	9,310.8	$ 7,212.5	2,136.0	(41.2)	3.5
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)
Issuance of restricted common stock	(0.4)		(0.4)
Stock compensation expense	4.7	4.7
Unearned compensation
Compensation expense recognized	0.1	0.1
Issuance of restricted common stock	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	327.9
Unearned compensation
Issuance of restricted common stock	2.6
Compensation expense recognized	0.0
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
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)
Issuance of restricted common stock	(0.6)		(0.6)
Stock compensation expense	6.6	6.6
Unearned compensation
Compensation expense recognized	0.1	0.1
Issuance of restricted common stock	1.3			1.3
Compensation expense recognized	0.0
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