INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Values of Securities (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Fair Value
Less than 12 months	$ 4,062	$ 4,990
12 months or more	8,802	2,547
Total	12,864	7,537
Gross Unrealized Losses
Less than 12 months	(372)	(94)
12 months or more	(995)	(67)
Total	(1,367)	(161)
U.S. Treasury and agency obligations
Fair Value
Less than 12 months	91	201
12 months or more	431	355
Total	522	556
Gross Unrealized Losses
Less than 12 months	(4)	(3)
12 months or more	(39)	(7)
Total	(43)	(10)
Mortgage-backed securities
Fair Value
Less than 12 months	1,109	2,082
12 months or more	1,785	556
Total	2,894	2,638
Gross Unrealized Losses
Less than 12 months	(129)	(49)
12 months or more	(263)	(20)
Total	(392)	(69)
Tax-exempt municipal securities
Fair Value
Less than 12 months	38	68
12 months or more	594	34
Total	632	102
Gross Unrealized Losses
Less than 12 months	(3)	(1)
12 months or more	(31)	(1)
Total	(34)	(2)
Residential
Fair Value
Less than 12 months	250	358
12 months or more	189	8
Total	439	366
Gross Unrealized Losses
Less than 12 months	(23)	(6)
12 months or more	(31)	0
Total	(54)	(6)
Commercial
Fair Value
Less than 12 months	282	295
12 months or more	1,191	400
Total	1,473	695
Gross Unrealized Losses
Less than 12 months	(11)	(4)
12 months or more	(98)	(7)
Total	(109)	(11)
Asset-backed securities
Fair Value
Less than 12 months	517	530
12 months or more	1,171	425
Total	1,688	955
Gross Unrealized Losses
Less than 12 months	(19)	(3)
12 months or more	(31)	(1)
Total	(50)	(4)
Corporate debt securities
Fair Value
Less than 12 months	1,775	1,456
12 months or more	3,441	769
Total	5,216	2,225
Gross Unrealized Losses
Less than 12 months	(183)	(28)
12 months or more	(502)	(31)
Total	$ (685)	$ (59)