Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Investment in marketable equity securities at cost	$ 75	$ 75
Investment securities available for sale at cost	9,955	9,967
Investment securities held to maturity at fair value	$ 8,993	$ 8,795
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Class A Common Stock
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	16,000,000	16,000,000
Common stock, shares issued (in shares)	13,514,808	13,501,017
Common stock, shares outstanding (in shares)	13,514,808	13,501,017
Class B Common Stock
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	2,000,000	2,000,000
Common stock, shares issued (in shares)	1,005,185	1,005,185
Common stock, shares outstanding (in shares)	1,005,185	1,005,185