FAIR VALUE MEASUREMENT - Items Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Items Measured at Fair Value on a Nonrecurring Basis
Non-marketable equity securities measured using the measurement alternative	$ 7,281	$ 7,337
Nonrecurring | Level 2
Items Measured at Fair Value on a Nonrecurring Basis
Loans held-for-sale	1,257	986
Other real estate owned	0	0
Loans	0	0
Non-marketable equity securities measured using the measurement alternative	0	104
Total assets	1,257	1,090
Nonrecurring | Level 3
Items Measured at Fair Value on a Nonrecurring Basis
Loans held-for-sale	1,260	1,312
Other real estate owned	7	11
Loans	147	144
Non-marketable equity securities measured using the measurement alternative	149	551
Total assets	1,563	2,018
Fair value | Nonrecurring
Items Measured at Fair Value on a Nonrecurring Basis
Loans held-for-sale	2,517	2,298
Other real estate owned	7	11
Loans	147	144
Non-marketable equity securities measured using the measurement alternative	149	655
Total assets	$ 2,820	$ 3,108