Changes in Fair Value of Assets Measured Using Significant Unobservable Inputs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	$ 36	$ 40	$ 38	$ 41
Realized in earnings	0	0	0	0
Unrealized in other comprehensive income	1	0	0	0
Purchases	0	0	0	0
Sales	0	(2)	0	(3)
Settlements	0	0	(1)	0
Ending Balance	37	38	37	38
Private Placements/Venture Capital
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	23	25	25	25
Realized in earnings	0	0	0	0
Unrealized in other comprehensive income	1	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	(1)	0
Ending Balance	24	25	24	25
Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	13	15	13	16
Realized in earnings	0	0	0	0
Unrealized in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Sales	0	(2)	0	(3)
Settlements	0	0	0	0
Ending Balance	$ 13	$ 13	$ 13	$ 13