Pension and Other Benefit Programs - Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation:
Benefit obligation at beginning of year	$ 875,000,000	$ 853,000,000
Interest cost	26,000,000	27,000,000	$ 27,000,000
Actuarial (gain) loss	(61,000,000)	44,000,000
Benefits paid	(49,000,000)	(49,000,000)
Benefit obligation at year end	791,000,000	875,000,000	853,000,000
Change in plan assets:
Fair value of plan assets at beginning of year	869,000,000	681,000,000
Actual return on plan assets	(26,000,000)	101,000,000
Contributions	0	136,000,000	10,000,000
Benefits paid	(49,000,000)	(49,000,000)
Fair value of plan assets at end of year	794,000,000	869,000,000	$ 681,000,000
Funded status	3,000,000	(6,000,000)
Accumulated benefit obligation	791,000,000	875,000,000
Amounts recognized in the accompanying consolidated balance sheets:
Accrued employee benefits	(204,000,000)	(243,000,000)
Accrued employee benefits
Amounts recognized in the accompanying consolidated balance sheets:
Accrued employee benefits	$ 3,000,000
Accrued employee benefits		$ (6,000,000)