Schedule of Investment Securities Classified as Current and Long-Term (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Amortized Cost	$ 9,451	$ 9,018
Gross Unrealized Gains	291	218
Gross Unrealized Losses	(64)	(126)
Fair Value	9,678	9,110
Debt Securities \| Tax-exempt municipal securities
Investment [Line Items]
Amortized Cost	2,967	2,611
Gross Unrealized Gains	74	61
Gross Unrealized Losses	(3)	(4)
Fair Value	3,038	2,668
Debt Securities \| Residential Mortgage-Backed Securities
Investment [Line Items]
Amortized Cost	11	13
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	11	13
Debt Securities \| Commercial Mortgage-Backed Securities
Investment [Line Items]
Amortized Cost	885	1,024
Gross Unrealized Gains	7	2
Gross Unrealized Losses	(33)	(41)
Fair Value	859	985
Debt Securities \| Asset-backed securities
Investment [Line Items]
Amortized Cost	252	264
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	(2)
Fair Value	253	263
Debt Securities \| Corporate debt securities
Investment [Line Items]
Amortized Cost	2,870	2,873
Gross Unrealized Gains	187	140
Gross Unrealized Losses	(27)	(55)
Fair Value	3,030	2,958
Debt Securities \| U.S. Treasury and other U.S. government corporations and agencies: \| U.S. Treasury and agency obligations
Investment [Line Items]
Amortized Cost	451	331
Gross Unrealized Gains	2	2
Gross Unrealized Losses	0	(1)
Fair Value	453	332
Debt Securities \| U.S. Treasury and other U.S. government corporations and agencies: \| Mortgage-backed securities
Investment [Line Items]
Amortized Cost	2,015	1,902
Gross Unrealized Gains	20	12
Gross Unrealized Losses	(1)	(23)
Fair Value	$ 2,034	$ 1,891

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

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-Publisher FASB
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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