Stock Repurchase Programs - Summary of Stock Repurchase Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		9 Months Ended
	Jul. 31, 2015	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Equity, Class of Treasury Stock [Line Items]
Repurchase of shares of common stock (in shares)			39
Repurchase of shares of common stock			$ 1,599
Shares Repurchased, Remaining Amount Authorized
Beginning balance		$ 985	985
Repurchase of shares of common stock			(1,512)	$ (3,476)
Ending balance			2,386
Stock Repurchase Program January 2015
Shares Repurchased, Remaining Amount Authorized
Authorization of additional plan		$ 2,000	$ 2,000
Shares Repurchase Prior To The Distribution
Equity, Class of Treasury Stock [Line Items]
Repurchase of shares of common stock (in shares)			18
Repurchase of shares of common stock (in usd per share)			$ 56.95
Repurchase of shares of common stock			$ 1,000
Shares Repurchased, Remaining Amount Authorized
Repurchase of shares of common stock			(1,000)
Stock Repurchase Program July 2015
Shares Repurchased, Remaining Amount Authorized
Authorization of additional plan	$ 1,000		$ 1,000
Shares Repurchase Subsequent To The Distribution
Equity, Class of Treasury Stock [Line Items]
Repurchase of shares of common stock (in shares)			21
Repurchase of shares of common stock (in usd per share)			$ 27.36
Repurchase of shares of common stock			$ 599
Shares Repurchased, Remaining Amount Authorized
Repurchase of shares of common stock			$ (599)