PARENT COMPANY ONLY FINANCIALS - Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS:
Cash and due from banks	$ 1,099	$ 1,171
Balances due from RBS	6	0
Other assets	2,841	2,384
TOTAL ASSETS	138,208	132,857
LIABILITIES:
Long-term borrowed funds	9,886	4,642
Other liabilities	1,490	1,606
TOTAL LIABILITIES	118,562	113,589
TOTAL STOCKHOLDERS’ EQUITY	19,646	19,268	$ 19,196	$ 24,129
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	138,208	132,857
Parent company
ASSETS:
Cash and due from banks	531	280
Other assets	154	214
TOTAL ASSETS	22,335	21,763
LIABILITIES:
Balances due	3	2
Other liabilities	90	143
TOTAL LIABILITIES	2,689	2,495
TOTAL STOCKHOLDERS’ EQUITY	19,646	19,268
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	22,335	21,763
Bank subsidiaries | Parent company
ASSETS:
Loans and advances	1,725	1,685
Investments in subsidiaries	19,865	19,512
Nonbank subsidiaries | Parent company
ASSETS:
Investments in subsidiaries	54	72
LIABILITIES:
Balances due	1	0
Unaffiliated companies | Parent company
LIABILITIES:
Long-term borrowed funds	1,345	350
Related bank holding companies | Parent company
LIABILITIES:
Long-term borrowed funds	$ 1,250	$ 2,000