Accumulated Other Comprehensive (Loss) Income (AOCI), Summary of AOCI Balances Including Amounts Reclassified from AOCI into Net Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 4,355
Ending Balance	4,553	$ 4,355
Foreign Currency Translation Adjustments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(101)	19	$ 142
Other comprehensive (loss) income before reclassifications, net of tax	(77)	(161)	(123)
Amounts reclassified from AOCI, net of tax	0	41	0
Net current period other comprehensive (loss) income	(77)	(120)	(123)
Ending Balance	(178)	(101)	19
Unrealized Gains (Losses) on Hedging Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(8)	(5)	1
Other comprehensive (loss) income before reclassifications, net of tax	3	(15)	(13)
Amounts reclassified from AOCI, net of tax	11	12	7
Net current period other comprehensive (loss) income	14	(3)	(6)
Ending Balance	6	(8)	(5)
Unrecognized (Losses) Gains and Prior Service Cost, Net [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(465)	(598)	(253)
Other comprehensive (loss) income before reclassifications, net of tax	(119)	81	(354)
Amounts reclassified from AOCI, net of tax	30	52	9
Net current period other comprehensive (loss) income	(89)	133	(345)
Ending Balance	(554)	(465)	(598)
Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(574)	(584)	(110)
Other comprehensive (loss) income before reclassifications, net of tax	(193)	(95)	(490)
Amounts reclassified from AOCI, net of tax	41	105	16
Net current period other comprehensive (loss) income	(152)	10	(474)
Ending Balance	$ (726)	$ (574)	$ (584)