INVESTMENT SECURITIES - Schedule of Contractual Maturities of Debt Securities Available for Sale (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost
Due within one year	$ 712
Due after one year through five years	2,872
Due after five years through ten years	2,661
Due after ten years	3,346
Mortgage and asset-backed securities	2,513
Amortized Cost	12,104	$ 9,826
Fair Value
Due within one year	711
Due after one year through five years	2,867
Due after five years through ten years	2,657
Due after ten years	3,567
Mortgage and asset-backed securities	2,500
Total debt securities	$ 12,302	$ 9,798