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, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss / (gain)	$ 6	$ 102	$ 51
Current year prior service cost (credit)	(9)	5	16
Total recognized in other comprehensive income (loss) (pre-tax)	(52)	$ 48	$ 15
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss / (gain)	14
Actuarial (loss) recognized during the year	(1)
Current year prior service cost (credit)	(15)
Prior service credit (cost) recognized during the year	16
Total recognized in other comprehensive income (loss) (pre-tax)	14
Total recognized in net periodic benefit costs and other comprehensive income (loss) (pre-tax)	21
United States Pension Benefits | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss / (gain)	(60)
Actuarial (loss) recognized during the year	(56)
Current year prior service cost (credit)	0
Prior service credit (cost) recognized during the year	2
Total recognized in other comprehensive income (loss) (pre-tax)	(114)
Total recognized in net periodic benefit costs and other comprehensive income (loss) (pre-tax)	(112)
Foreign Pension Benefits | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current year actuarial loss / (gain)	52
Actuarial (loss) recognized during the year	(10)
Current year prior service cost (credit)	6
Prior service credit (cost) recognized during the year	0
Total recognized in other comprehensive income (loss) (pre-tax)	48
Total recognized in net periodic benefit costs and other comprehensive income (loss) (pre-tax)	$ 58