PARENT COMPANY FINANCIALS - Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS:
Cash and due from banks	$ 987	$ 955
Other assets	3,429	2,993
TOTAL ASSETS	152,336	149,520
LIABILITIES:
Long-term borrowed funds	11,765	12,790
Other liabilities	1,660	1,447
TOTAL LIABILITIES	132,066	129,773
TOTAL STOCKHOLDERS’ EQUITY	20,270	19,747	$ 19,646	$ 19,268
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	152,336	149,520
Parent company
ASSETS:
Cash and due from banks	563	671
Other assets	125	128
TOTAL ASSETS	22,756	22,141
LIABILITIES:
Other liabilities	166	76
TOTAL LIABILITIES	2,486	2,394
TOTAL STOCKHOLDERS’ EQUITY	20,270	19,747
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	22,756	22,141
Bank subsidiaries | Parent company
ASSETS:
Loans and advances	1,160	1,156
Investments in subsidiaries	20,765	20,116
Unaffiliated companies | Parent company
LIABILITIES:
Long-term borrowed funds	2,320	2,318
Nonbank subsidiaries | Parent company
ASSETS:
Loans and advances	70	20
Investments in subsidiaries	$ 73	$ 50