Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	$ 12,330	$ 12,230
Equity Securities, FV-NI, Cost	4,167	4,121
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 309	$ 303
Common Stock, Par or Stated Value Per Share	$ 2	$ 2
Common Stock, Shares Authorized	500.0	500.0
Common Stock, Shares, Issued	198.3	198.3
Treasury Stock, Shares	38.0	38.0