Stock Repurchase Program - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Jun. 30, 2015	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Repurchase of shares of common stock (in shares)			59,000,000
Repurchase of shares of common stock			$ 2,100
Stock repurchase, remaining amount authorized			$ 1,836	$ 985
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
Stock Repurchase Program January 2015
Equity, Class of Treasury Stock [Line Items]
Authorization of additional plan		$ 2,000	$ 2,000
Stock Repurchase Program June 2015
Equity, Class of Treasury Stock [Line Items]
Authorization of additional plan	$ 1,000		$ 1,000