Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income Loss) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Foreign currency translation adjustments (net of deferred tax adjustments of $(9) in 2016 and deferred tax adjustments of $8 in 2015, respectively)	$ (1,880)	$ (1,102)
Net unrealized investment gains (net of deferred tax liability of $10 in 2016 and $2 in 2015)	19	6
Net charges related to pension / post-retirement plans (net of deferred tax asset of $1,530 and $1,519 in 2016 and 2015, respectively)	(3,232)	(3,124)
Accumulated other comprehensive loss	$ (5,093)	$ (4,220)