Pension and Other Benefit Programs - Effect on Accumulated Other Comprehensive Income (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized net actuarial losses (gains), after tax	$ 90
Loss (gain) recognition	1
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized net actuarial losses (gains), after tax	108
Loss (gain) recognition	2
SERP Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized net actuarial losses (gains), after tax	4
Loss (gain) recognition	0
Post-retirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized net actuarial losses (gains), after tax	(22)
Loss (gain) recognition	$ (1)