Shareholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended		12 Months Ended	19 Months Ended								12 Months Ended	24 Months Ended	1 Months Ended
	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014	Jul. 30, 2014	Apr. 17, 2014	Feb. 06, 2014	Aug. 01, 2013	May 30, 2013	Feb. 28, 2013	Nov. 30, 2006	Dec. 31, 2014 Scenario, Forecast	Dec. 31, 2014 Scenario, Forecast	Nov. 30, 2006 Sold Warrants	Mar. 17, 2014 Warrant
Sold warrants to acquire shares of our common stock															215,000,000
Sold warrants to acquire shares of our common stock, exercise price per share												$ 19.55
Warrants exercised																$ 109,000,000
Common stock excluded from calculation of diluted earnings per share	1,000,000	3,000,000	3,000,000
Repurchases of Common Stock, shares authorized to repurchase											250,000,000
Total Repurchases of Common Stock, cost		1,400,000,000			3,700,000,000
Total Repurchases of Common Stock, shares		52,000,000			146,000,000
Shares authorized for future repurchases		104,000,000			104,000,000
Payments for Repurchase of Common Stock		$ 1,374,000,000	$ 1,965,000,000	$ 3,000,000,000									$ 3,000,000,000	$ 6,000,000,000
Approved dividend (in usd per share)						$ 0.115	$ 0.115	$ 0.10	$ 0.10	$ 0.10