Subsequent Events - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Subsequent Event
Amount	$ (99)	$ (125)
Subsequent events
Subsequent Event
Issuance date	Apr. 25, 2014
Issue of senior notes to third party investors	1,500
Subsequent events | March 2014 Repurchase Program
Subsequent Event
Total shares repurchased	6,216,480
Amount	150
Redemption date	May 01, 2014
Subsequent events | Fixed rate 2.375% senior notes due 2019
Subsequent Event
Maturity date	Apr. 25, 2019
Issue of senior notes to third party investors	850
Subsequent events | Fixed rate 1.35% notes due 2017
Subsequent Event
Maturity date	Jun. 01, 2017
Issue of senior notes to third party investors	$ 650