Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Amortized Cost	$ 12,263.0
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	75,000,000	75,000,000
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	278,392,263	296,932,316
Common Class B [Member]
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	0	0