Stockholders' Equity Activity (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Document Fiscal Year Focus			2016
Treasury Stock, Shares, Acquired			583,340
Stock Issued During Period, Shares, New Issues	34,500,000	25,300,000
Proceeds from Issuance of Common Stock	$ 776	$ 815	$ 779	$ 819	$ 6
Common Stock, Shares Authorized		200,000,000	300,000,000	300,000,000