Stockholders' Equity Stockholder's Equity (Schedule of Components of Other Comprehensive Income / (Loss)) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax benefit (expense) recorded in Stockholders' Equity	$ 33	$ (138)	$ 1,461
Tax benefits associated with stock compensation programs	$ 21	$ 37	$ 58