Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Allowance for loans losses	$ 832	$ 1,022
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,125,000,000	1,125,000,000
Common stock, shares issued	464,000,000	461,000,000
Tax expense for accumulated other comprehensive loss	$ 6	$ 29
Common stock held in treasury	350,000,000	331,000,000
Series A Junior Participating Preferred Stock [Member]
Preferred stock, par value	$ 0.2	$ 0.2
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
FFELP Loans [Member]
Allowance for loans losses	$ 215	$ 222
Private Education Loans [Member]
Allowance for loans losses	$ 617	$ 800