Debt - Components of Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Long-Term Debt
Long-term debt principal	$ 4,022.7	$ 4,309.3
Net unamortized discount, premium and debt issuance costs	(25.7)	(29.1)
Long-term debt carrying amount	$ 3,997.0	$ 4,280.2
3.3% notes payable, due 2022
Long-Term Debt
Interest rate (as a percent)		3.30%
Long-term debt principal		$ 300.0
Net unamortized discount, premium and debt issuance costs		(0.3)
Long-term debt carrying amount		$ 299.7
3.125% notes payable, due 2023
Long-Term Debt
Interest rate (as a percent)	3.125%	3.125%
Long-term debt principal	$ 300.0	$ 300.0
Net unamortized discount, premium and debt issuance costs	(0.1)	(0.4)
Long-term debt carrying amount	$ 299.9	$ 299.6
3.4% notes payable, due 2025
Long-Term Debt
Interest rate (as a percent)	3.40%	3.40%
Long-term debt principal	$ 400.0	$ 400.0
Net unamortized discount, premium and debt issuance costs	(1.2)	(1.7)
Long-term debt carrying amount	$ 398.8	$ 398.3
3.1% notes payable, due 2026
Long-Term Debt
Interest rate (as a percent)	3.10%	3.10%
Long-term debt principal	$ 350.0	$ 350.0
Net unamortized discount, premium and debt issuance costs	(1.4)	(1.9)
Long-term debt carrying amount	$ 348.6	$ 348.1
3.7% notes payable, due 2029
Long-Term Debt
Interest rate (as a percent)	3.70%	3.70%
Long-term debt principal	$ 500.0	$ 500.0
Net unamortized discount, premium and debt issuance costs	(4.3)	(5.0)
Long-term debt carrying amount	$ 495.7	$ 495.0
2.125% notes payable, due 2030
Long-Term Debt
Interest rate (as a percent)	2.125%	2.125%
Long-term debt principal	$ 600.0	$ 600.0
Net unamortized discount, premium and debt issuance costs	(3.6)	(4.1)
Long-term debt carrying amount	$ 596.4	$ 595.9
6.05% notes payable, due 2036
Long-Term Debt
Interest rate (as a percent)	6.05%	6.05%
Long-term debt principal	$ 505.6	$ 505.6
Net unamortized discount, premium and debt issuance costs	(2.3)	(2.3)
Long-term debt carrying amount	$ 503.3	$ 503.3
4.625% notes payable, due 2042
Long-Term Debt
Interest rate (as a percent)	4.625%	4.625%
Long-term debt principal	$ 300.0	$ 300.0
Net unamortized discount, premium and debt issuance costs	(2.9)	(3.0)
Long-term debt carrying amount	$ 297.1	$ 297.0
4.35% notes payable, due 2043
Long-Term Debt
Interest rate (as a percent)	4.35%	4.35%
Long-term debt principal	$ 300.0	$ 300.0
Net unamortized discount, premium and debt issuance costs	(3.0)	(3.0)
Long-term debt carrying amount	$ 297.0	$ 297.0
4.3% notes payable, due 2046
Long-Term Debt
Interest rate (as a percent)	4.30%	4.30%
Long-term debt principal	$ 300.0	$ 300.0
Net unamortized discount, premium and debt issuance costs	(3.1)	(3.1)
Long-term debt carrying amount	296.9	296.9
Floating rate notes payable, due 2055
Long-Term Debt
Long-term debt principal	400.0	400.0
Net unamortized discount, premium and debt issuance costs	(4.5)	(4.6)
Long-term debt carrying amount	395.5	395.4
Mortgages and notes payable | Non-recourse
Long-Term Debt
Long-term debt principal	67.1	53.7
Net unamortized discount, premium and debt issuance costs	0.7	0.3
Long-term debt carrying amount	$ 67.8	$ 54.0