Stockholders' Equity (Schedule of Components of Other Comprehensive Income / (Loss)) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax (expense) benefit recorded in Stockholders' Equity	$ (138)	$ 1,461	$ (1,617)
Tax benefits associated with stock compensation programs	$ 37	$ 58	$ 48