Capital Actions (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Capital Actions
Shares acquired for treasury	$ 180	$ 99
October 20, 2014 ASR | March 2014 Repurchase Program
Capital Actions
Repurchase date	Oct. 23, 2014
Shares acquired for treasury	180
Shares repurchased on repurchase date	8,337,875
Shares received from forward contract settlement	794,245
Total shares repurchased	9,132,120
Settlement date	Jan. 08, 2015
January 22, 2015 ASR | March 2014 Repurchase Program
Capital Actions
Repurchase date	Jan. 27, 2015
Shares acquired for treasury	$ 180
Shares repurchased on repurchase date	8,542,713
Shares received from forward contract settlement	1,103,744
Total shares repurchased	9,646,457
Settlement date	Apr. 28, 2015