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INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Values of Securities (Detail) - USD ($) $ in Millions | Jun. 30, 2017 | Dec. 31, 2016
--- | --- | ---
Investment [Line Items] |  |
Less than 12 months, Fair Value | $ 5,244 | $ 6,758
Less than 12 months, Gross Unrealized Losses | (93) | (187)
12 months or more, Fair Value | 114 | 209
12 months or more, Gross Unrealized Losses | (4) | (9)
Total, Fair Value | 5,358 | 6,967
Total, Gross Unrealized Losses | (97) | (196)
Debt Securities | Tax-exempt municipal securities |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 1,898 | 2,756
Less than 12 months, Gross Unrealized Losses | (20) | (67)
12 months or more, Fair Value | 39 | 43
12 months or more, Gross Unrealized Losses | (1) | (1)
Total, Fair Value | 1,937 | 2,799
Total, Gross Unrealized Losses | (21) | (68)
Debt Securities | Residential Mortgage-Backed Securities |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 0 | 0
Less than 12 months, Gross Unrealized Losses | 0 | 0
12 months or more, Fair Value | 4 | 4
12 months or more, Gross Unrealized Losses | 0 | 0
Total, Fair Value | 4 | 4
Total, Gross Unrealized Losses | 0 | 0
Debt Securities | Commercial Mortgage-Backed Securities |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 99 | 182
Less than 12 months, Gross Unrealized Losses | (2) | (3)
12 months or more, Fair Value | 1 | 24
12 months or more, Gross Unrealized Losses | 0 | (1)
Total, Fair Value | 100 | 206
Total, Gross Unrealized Losses | (2) | (4)
Debt Securities | Asset-backed securities |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 92 | 51
Less than 12 months, Gross Unrealized Losses | 0 | 0
12 months or more, Fair Value | 0 | 63
12 months or more, Gross Unrealized Losses | 0 | 0
Total, Fair Value | 92 | 114
Total, Gross Unrealized Losses | 0 | 0
Debt Securities | Corporate debt securities |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 1,200 | 1,544
Less than 12 months, Gross Unrealized Losses | (37) | (71)
12 months or more, Fair Value | 64 | 69
12 months or more, Gross Unrealized Losses | (3) | (7)
Total, Fair Value | 1,264 | 1,613
Total, Gross Unrealized Losses | (40) | (78)
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 645 | 697
Less than 12 months, Gross Unrealized Losses | (9) | (15)
12 months or more, Fair Value | 3 | 3
12 months or more, Gross Unrealized Losses | 0 | 0
Total, Fair Value | 648 | 700
Total, Gross Unrealized Losses | (9) | (15)
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities |  |
Investment [Line Items] |  |
Less than 12 months, Fair Value | 1,310 | 1,528
Less than 12 months, Gross Unrealized Losses | (25) | (31)
12 months or more, Fair Value | 3 | 3
12 months or more, Gross Unrealized Losses | 0 | 0
Total, Fair Value | 1,313 | 1,531
Total, Gross Unrealized Losses | $ (25) | $ (31)

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