Fair Value of Financial Assets and Liabilities - Unrealized Losses on Investments by Investment Category and Length of Time in Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 2,559	$ 912
Less Than 12 Months, Gross Unrealized Losses	(11)	(2)
12 Months or Greater, Fair Value	128	97
12 Months or Greater, Gross Unrealized Losses	(4)	(5)
Total, Fair Value	2,687	1,009
Total, Gross Unrealized Losses	(15)	(7)
U.S. government and agency obligations
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	1,161	188
Less Than 12 Months, Gross Unrealized Losses	(3)	(1)
12 Months or Greater, Fair Value	20	12
12 Months or Greater, Gross Unrealized Losses	0	0
Total, Fair Value	1,181	200
Total, Gross Unrealized Losses	(3)	(1)
U.S. corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	532	266
Less Than 12 Months, Gross Unrealized Losses	(2)	0
12 Months or Greater, Fair Value	17	0
12 Months or Greater, Gross Unrealized Losses	0	0
Total, Fair Value	549	266
Total, Gross Unrealized Losses	(2)	0
High yield corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	120	21
Less Than 12 Months, Gross Unrealized Losses	(3)	0
12 Months or Greater, Fair Value	0	1
12 Months or Greater, Gross Unrealized Losses	0	(1)
Total, Fair Value	120	22
Total, Gross Unrealized Losses	(3)	(1)
Municipal obligations
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	51	258
Less Than 12 Months, Gross Unrealized Losses	0	0
12 Months or Greater, Fair Value	0	12
12 Months or Greater, Gross Unrealized Losses	0	0
Total, Fair Value	51	270
Total, Gross Unrealized Losses	0	0
Auction rate securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	0	0
Less Than 12 Months, Gross Unrealized Losses	0	0
12 Months or Greater, Fair Value	60	70
12 Months or Greater, Gross Unrealized Losses	(3)	(4)
Total, Fair Value	60	70
Total, Gross Unrealized Losses	(3)	(4)
Foreign debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	695	178
Less Than 12 Months, Gross Unrealized Losses	(3)	0
12 Months or Greater, Fair Value	6	2
12 Months or Greater, Gross Unrealized Losses	0	0
Total, Fair Value	701	180
Total, Gross Unrealized Losses	(3)	0
Publicly traded equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	0	1
Less Than 12 Months, Gross Unrealized Losses	0	(1)
12 Months or Greater, Fair Value	25	0
12 Months or Greater, Gross Unrealized Losses	(1)	0
Total, Fair Value	25	1
Total, Gross Unrealized Losses	$ (1)	$ (1)