Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	$ 14,709	$ 14,361
Equity Securities, FV-NI, Cost	4,313	4,282
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 331	$ 337
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 2	$ 2
Common Stock, Shares Authorized (in shares)	500.0	500.0
Common Stock, Shares, Issued (in shares)	198.3	198.3
Treasury Stock, Common, Shares (in shares)	41.8	41.3