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INVESTMENT SECURITIES - Securities Classified as Current and Long-Term (Detail) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Investment [Line Items]    
Amortized Cost $ 12,213 $ 12,104
Gross Unrealized Gains 139 286
Gross Unrealized Losses (249) (88)
Fair Value 12,103 12,302
Debt Securities | Tax-exempt municipal securities    
Investment [Line Items]    
Amortized Cost 3,549 3,884
Gross Unrealized Gains 6 33
Gross Unrealized Losses (61) (28)
Fair Value 3,494 3,889
Debt Securities | Residential Mortgage-Backed Securities    
Investment [Line Items]    
Amortized Cost 24 26
Gross Unrealized Gains 0 0
Gross Unrealized Losses (1) 0
Fair Value 23 26
Debt Securities | Commercial Mortgage-Backed Securities    
Investment [Line Items]    
Amortized Cost 580 455
Gross Unrealized Gains 0 3
Gross Unrealized Losses (11) (2)
Fair Value 569 456
Debt Securities | Asset-backed securities    
Investment [Line Items]    
Amortized Cost 554 407
Gross Unrealized Gains 1 1
Gross Unrealized Losses (1) 0
Fair Value 554 408
Debt Securities | Corporate debt securities    
Investment [Line Items]    
Amortized Cost 4,693 5,175
Gross Unrealized Gains 131 244
Gross Unrealized Losses (114) (37)
Fair Value 4,710 5,382
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations    
Investment [Line Items]    
Amortized Cost 505 532
Gross Unrealized Gains 1 1
Gross Unrealized Losses (5) (2)
Fair Value 501 531
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities    
Investment [Line Items]    
Amortized Cost 2,308 1,625
Gross Unrealized Gains 0 4
Gross Unrealized Losses (56) (19)
Fair Value $ 2,252 $ 1,610