INVESTMENT SECURITIES - Contractual Maturities (Details) $ in Millions	Jun. 30, 2020 USD ($)
Amortized cost
Within one year	$ 643
After one year through five years	2,483
After five years through ten years	6,516
After ten years	20,575
Estimated fair value
Within one year	657
After one year through five years	2,676
After five years through ten years	7,599
After ten years	$ 26,261