Stock Repurchase Programs - Additional Information (Details) - USD ($)	1 Months Ended		9 Months Ended
	Jul. 31, 2015	Jan. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Jan. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Repurchase of shares of common stock (in shares)			39,000,000
Repurchase of shares of common stock			$ 1,599,000,000
Stock Repurchase remaining amount authorized			$ 2,386,000,000	$ 985,000,000
Treasury shares retired (in shares)			0
Stock Repurchase Program January 2014
Equity, Class of Treasury Stock [Line Items]
Amount authorized under stock repurchase program					$ 5,000,000,000
Stock Repurchase Program January 2015
Equity, Class of Treasury Stock [Line Items]
Authorization of additional plan		$ 2,000,000,000	$ 2,000,000,000
Stock Repurchase Program July 2015
Equity, Class of Treasury Stock [Line Items]
Authorization of additional plan	$ 1,000,000,000		$ 1,000,000,000