Retirement and Employee Benefit Plans (Pension and Other Postretirement Benefit Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Curtailment (gain) loss		$ (4)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	10	$ 9
Interest cost	5	5	5
Expected return on plan assets	(6)	(7)	(6)
Amortization of transition obligation	0	0	0
Amortization of prior service cost	0	0	0
Amortization of net loss	2	2	2
Net periodic benefit cost	8	10	10
Curtailment (gain) loss	0	0	0
Settlement loss	6	0	0
Net periodic benefit cost	14	10	10
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2	2
Interest cost	0	1	0
Expected return on plan assets	0	0	0
Amortization of transition obligation	0	0	0
Amortization of prior service cost	0	0	0
Amortization of net loss	0	0	0
Net periodic benefit cost	1	3	2
Curtailment (gain) loss	0	(4)	0
Settlement loss	0	0	0
Net periodic benefit cost	$ 1	$ (1)	$ 2