Debt - Narrative (Details) - USD ($)			1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 10, 2022	Jun. 04, 2019	Mar. 31, 2021	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Feb. 15, 2022	Sep. 22, 2020	Jun. 08, 2018	Feb. 28, 2015
Debt Instrument [Line Items]
Long-term Debt				$ 1,388,100,000		$ 1,388,100,000		$ 1,386,900,000
Interest and other expenses				14,000,000	$ 14,000,000	28,100,000	$ 26,700,000
Interest paid, including capitalized interest, operating and investing activities				2,500,000	$ 2,400,000	27,300,000	$ 24,400,000
Derivative, Gain on Derivative						5,900,000
2.400% Senior Notes due September 30, 2030
Debt Instrument [Line Items]
Long-term Debt										$ 395,800,000
Senior Notes, 3.800 Percent Due February 23, 2033
Debt Instrument [Line Items]
Long-term Debt									$ 395,100,000
5.875% Fixed-Rate Reset Junior Subordinated Debentures due 2062
Debt Instrument [Line Items]
Long-term Debt	$ 144,700,000
Senior Notes | 4.350% Senior Notes due February 15, 2025
Debt Instrument [Line Items]
Long-term Debt				$ 449,500,000		$ 449,500,000		449,300,000
Stated interest rate				4.35%		4.35%
Long-term debt, gross				$ 450,000,000		$ 450,000,000
Face amount of debt												$ 250,000,000
Increase in senior notes			$ 200,000,000
Senior Notes | 2.400% Senior Notes due September 30, 2030
Debt Instrument [Line Items]
Long-term Debt				396,800,000		396,800,000		396,600,000
Stated interest rate										2.40%
Long-term debt, gross				400,000,000		400,000,000
Effective interest rate										2.52%
Senior Notes | Senior Notes, 3.800 Percent Due February 23, 2033
Debt Instrument [Line Items]
Long-term Debt				395,700,000		395,700,000		395,500,000
Stated interest rate									3.80%
Long-term debt, gross				400,000,000		400,000,000
Effective interest rate										3.95%
Senior Notes | 5.875% Fixed-Rate Reset Junior Subordinated Debentures due 2062
Debt Instrument [Line Items]
Long-term debt, gross				150,000,000		150,000,000
Senior Notes | Senior Notes, 5.875 Percent Due March 15, 2062
Debt Instrument [Line Items]
Long-term Debt				146,100,000		146,100,000		$ 145,500,000
Junior Debt | Senior Notes, 5.875 Percent Due March 15, 2062
Debt Instrument [Line Items]
Stated interest rate	5.875%
Junior Debt | Senior Notes, 5.875 Percent Due March 15, 2062 | Five-Year Treasury Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	4.14%
Revolving Credit Facility | Notes Payable under Revolving Credit Agreement | Second Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 800,000,000		460,000,000		460,000,000					$ 600,000,000
Increase in revolving credit borrowing capacity		$ 200,000,000
Line of credit facility, amount outstanding				$ 0		$ 0