PREMISES, EQUIPMENT, AND SOFTWARE - Schedule of Amortization (Details) $ in Millions	Dec. 31, 2018 USD ($)
Capitalized Software, Expected Future Amortization Expense [Abstract]
2019	$ 186
2020	155
2021	116
2022	80
2023	48
Thereafter	72
Total	657	[1]
In-process software	$ 188

[1] Excluded from this balance is $188 million of in-process software at December 31, 2018.