CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)		Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Debt securities available for sale, amortized cost		$ 3,110,000,000	$ 3,380,000,000
Debt securities available for sale, allowance for credit losses		0	0
Debt securities held-to-maturity, fair value		3,114,000,000	2,973,000,000
Debt securities held to maturity, allowance for credit losses		40,000.00	40,000.00
Loans held for sale, fair value	[1]	165,000,000	144,000,000
Unearned income on loans		$ 93,000,000	$ 77,000,000
Preferred stock, par value (in dollars per share)		$ 0.01	$ 0.01
Preferred stock, liquidation preference per share (in dollars per share)		$ 1,000	$ 1,000
Preferred stock, shares authorized		20,000,000	20,000,000
Preferred stock, shares issued		110,877	110,877
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized		500,000,000	500,000,000
Common stock, shares issued		328,213,157	328,057,368
Treasury stock, shares		9,516,731	6,427,839

[1] Amount represents loans for which we have elected the fair value option. See Note 18.