INVESTMENT SECURITIES - Investment Securities Classified as Current and Long-Term (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost to Fair Value
Amortized Cost	$ 11,160	$ 10,641
Gross Unrealized Gains	219	9
Gross Unrealized Losses	(8)	(213)
Fair Value	11,371	10,437
U.S. Treasury and agency obligations
Amortized Cost to Fair Value
Amortized Cost	353	419
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	(3)
Fair Value	354	417
Mortgage-backed securities
Amortized Cost to Fair Value
Amortized Cost	3,628	2,595
Gross Unrealized Gains	85	3
Gross Unrealized Losses	(3)	(54)
Fair Value	3,710	2,544
Tax-exempt municipal securities
Amortized Cost to Fair Value
Amortized Cost	1,433	2,805
Gross Unrealized Gains	30	3
Gross Unrealized Losses	0	(37)
Fair Value	1,463	2,771
Residential mortgage-backed securities
Amortized Cost to Fair Value
Amortized Cost		55
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		55
Commercial mortgage-backed securities
Amortized Cost to Fair Value
Amortized Cost	786	537
Gross Unrealized Gains	18	0
Gross Unrealized Losses	0	(14)
Fair Value	804	523
Asset-backed securities
Amortized Cost to Fair Value
Amortized Cost	1,093	991
Gross Unrealized Gains	3	1
Gross Unrealized Losses	(3)	(7)
Fair Value	1,093	985
Corporate debt securities
Amortized Cost to Fair Value
Amortized Cost	3,867	3,239
Gross Unrealized Gains	82	1
Gross Unrealized Losses	(2)	(98)
Fair Value	$ 3,947	$ 3,142

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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