Share Repurchase Program and Dividend - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions				1 Months Ended			3 Months Ended		9 Months Ended
	Jul. 14, 2015	Feb. 10, 2015	Jan. 27, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 2,000,000,000	$ 2,000,000,000
Share repurchase program completion date			Sep. 30, 2015	Dec. 31, 2016
Cash dividends declared per common share				$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.30	$ 0.10
Dividends payable, record date				Aug. 10, 2015	May 04, 2015	Feb. 09, 2015
Dividends payable, payable date				Aug. 24, 2015	May 18, 2015	Feb. 23, 2015
Total cash payment for dividends							$ 67,000,000		$ 206,000,000
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchased (in shares)	0.1	0.1					38.4		59.5
Aggregate stock repurchase price	$ 2,000,000	$ 4,000,000					$ 1,600,000,000		$ 2,500,000,000
Average cost per share							$ 40.56		$ 42.00