SECURITIES - Amortized Cost and Fair Value of Securities, by Contractual Maturities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Securities [Line Items]
Available for sale, due in one year or less, amortized cost	$ 9
Available for sale, due after one year but within five years, amortized cost	434
Available for sale, due after five years but within ten years, amortized cost	106
Available for sale, due after ten years, amortized cost	55
Available for sale, with contractual maturities, amortized cost	604
Amortized Cost	3,600	$ 3,416
Available for sale, due in one year or less, fair value	9
Available for sale, due after one year but within five years, fair value	412
Available for sale, due after five years but within ten years, fair value	105
Available for sale, due after ten years, fair value	56
Available for sale, with contractual maturities, fair value	582
Fair Value	3,446	3,426
Held to maturity, due in one year or less, amortized cost	1
Held to maturity, due after one year but within five years, amortized cost	23
Held to maturity, due after five years but within ten years, amortized cost	141
Held to maturity, due after ten years, amortized cost	816
Held to maturity, with contractual maturities, amortized cost	981
Amortized Cost	3,513	3,463
Held to maturity, due in one year or less, fair value	1
Held to maturity, due after one year but within five years, fair value	23
Held to maturity, due after five years but within ten years, fair value	137
Held to maturity, due after ten years, fair value	794
Held to maturity, with contractual maturities, fair value	955
Held to maturity, fair value	3,364	3,506
Agency mortgage-backed securities
Schedule Of Securities [Line Items]
Available-for-sale, amortized cost	1,440
Amortized Cost	1,440	1,342
Available for sale, fair value	1,387
Fair Value	1,387	1,357
Held to maturity, amortized cost	1,261
Amortized Cost	1,261	1,191
Held to maturity, fair value	1,209
Held to maturity, fair value	1,209	1,201
Agency collateralized mortgage obligations
Schedule Of Securities [Line Items]
Available-for-sale, amortized cost	1,236
Amortized Cost	1,236	1,192
Available for sale, fair value	1,169
Fair Value	1,169	1,186
Held to maturity, amortized cost	943
Amortized Cost	943	930
Held to maturity, fair value	888
Held to maturity, fair value	888	923
Commercial mortgage-backed securities
Schedule Of Securities [Line Items]
Available-for-sale, amortized cost	320
Amortized Cost	320	294
Available for sale, fair value	308
Fair Value	308	297
Held to maturity, amortized cost	328
Amortized Cost	328	323
Held to maturity, fair value	312
Held to maturity, fair value	$ 312	$ 324

Schedule Of Securities [Line Items]

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