Pension and Other Benefit Programs - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions	$ 0	$ 136,000,000	$ 10,000,000
Amount pending settlement	$ 25,000,000
Period of amortization	4 years
Corridor approach percentage	10.00%
Net periodic post-retirement benefit costs	$ 1,000,000	$ (15,000,000)	(16,000,000)
Discount rate	4.00%	3.40%
Weighted-average discount rate for determining interest costs (pension/SERP plans)	3.00%	3.20%
Health care cost trend rate assumed	7.20%
Ultimate health care cost trend rate	4.50%
Contribution plan cost	$ 39,000,000	$ 38,000,000	31,000,000
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash surrender value of life insurance	57,000,000	55,000,000
Net periodic post-retirement benefit costs	1,000,000	1,000,000	1,000,000
Post-retirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic post-retirement benefit costs	5,000,000	$ 5,000,000	$ 7,000,000
Anticipated medicare subsidy receipts	$ 13,000,000
Equity securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		5.00%	65.00%
Fixed income securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		95.00%	35.00%