Fair Value of Financial Assets and Liabilities - Unrealized Losses on Investments by Investment Category and Length of Time in Continuous Unrealized Loss Position (Detail) $ in Millions	Jun. 30, 2016 USD ($)
Gain (Loss) on Investments [Line Items]
Less Than 12 Months Fair Value	$ 150
Less than 12 Months Gross Unrealized Losses	(3)
12 Months or Greater Fair Value	17
12 Months or Greater Gross Unrealized Losses	(8)
Total Fair Value	167
Total, Gross Unrealized Losses	(11)
U.S. government and agency obligations
Gain (Loss) on Investments [Line Items]
Less Than 12 Months Fair Value	128
Less than 12 Months Gross Unrealized Losses	(1)
12 Months or Greater Fair Value	0
12 Months or Greater Gross Unrealized Losses	0
Total Fair Value	128
Total, Gross Unrealized Losses	(1)
High yield corporate debt securities
Gain (Loss) on Investments [Line Items]
Less Than 12 Months Fair Value	20
Less than 12 Months Gross Unrealized Losses	(1)
12 Months or Greater Fair Value	15
12 Months or Greater Gross Unrealized Losses	(1)
Total Fair Value	35
Total, Gross Unrealized Losses	(2)
Publicly traded equity securities
Gain (Loss) on Investments [Line Items]
Less Than 12 Months Fair Value	2
Less than 12 Months Gross Unrealized Losses	(1)
12 Months or Greater Fair Value	2
12 Months or Greater Gross Unrealized Losses	(7)
Total Fair Value	4
Total, Gross Unrealized Losses	$ (8)