Stock Repurchase Programs - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Jun. 30, 2015	Jan. 31, 2015	Mar. 31, 2016	Dec. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Stock repurchase remaining amount authorized			$ 836	$ 1,836
Treasury shares retired (in shares)			0
Stock Repurchase Program January 2015
Equity, Class of Treasury Stock [Line Items]
Authorization of additional plan		$ 2,000
Stock Repurchase Program June 2015
Equity, Class of Treasury Stock [Line Items]
Authorization of additional plan	$ 1,000