Retirement and Employee Benefit Plans (Amounts Recognized in Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017	[1]
Defined Benefit Plan Disclosure [Line Items]
Total change in value of pension and postretirement liabilities	$ 3	$ 8	[1]	$ (11)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss arising during the year	(5)	(2)
Amortization of prior service cost	0	0
Amortization of net loss	2	2
Settlements	8	0
Curtailments	0	5
Tax effect	(1)	(1)
Total change in value of pension and postretirement liabilities	4	4
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss arising during the year	(1)	0
Amortization of prior service cost	0	0
Amortization of net loss	0	0
Settlements	0	0
Curtailments	0	3
Tax effect	0	(1)
Total change in value of pension and postretirement liabilities	$ (1)	$ 2

[1] In 2018 and 2017, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.