Pension and Other Postretirement Benefit Plans (Other Changes in Plan Assets and Benefit Obligations Recognized in OCI (Pre-Tax) in 2011) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	$ 51	$ 139	$ 55
Total recognized in other comprehensive loss (pre-tax)	15	$ 70	$ 79
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	14
Actuarial (loss) recognized during the year	0
Current year prior service cost (credit)	16
Prior service credit (cost) recognized during the year	4
Total recognized in other comprehensive loss (pre-tax)	34
Total recognized in net periodic benefit costs and other comprehensive loss (pre-tax)	57
United States Pension Benefits | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	4
Actuarial (loss) recognized during the year	(50)
Current year prior service cost (credit)	0
Prior service credit (cost) recognized during the year	3
Total recognized in other comprehensive loss (pre-tax)	(43)
Total recognized in net periodic benefit costs and other comprehensive loss (pre-tax)	(35)
Foreign Pension Benefits | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss	33
Actuarial (loss) recognized during the year	(9)
Current year prior service cost (credit)	0
Prior service credit (cost) recognized during the year	0
Total recognized in other comprehensive loss (pre-tax)	24
Total recognized in net periodic benefit costs and other comprehensive loss (pre-tax)	$ 30