Retirement and Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan cost	$ 2.0	$ 2.0	$ 2.0
Contributions capitalized	2.0	1.0	1.0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	$ 11.0
Defined benefit plan, assumptions used calculating benefit obligation, weighted-average interest crediting rate	6.00%
Defined benefit plan included in accumulated other comprehensive (income) loss, before tax	$ 23.0	36.0
Defined benefit plan included in accumulated other comprehensive (income) loss after tax	18.0	28.0
Total change in value of pension and postretirement liabilities	(13.0)	5.0	(3.0)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Non-cash curtailment gain	0.0	0.0	0.0
Settlement loss	2.0	0.0	6.0
Settlements	8.0	0.0	21.0
Decrease for remeasurement due to Settlement	4.0
Total change in value of pension and postretirement liabilities	(11.0)	5.0
Employer contributions	12.0	12.0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Non-cash curtailment gain	0.0	0.0	0.0
Settlement loss	0.0	0.0	$ 0.0
Settlements	0.0	0.0
Total change in value of pension and postretirement liabilities	(2.0)	(1.0)
Employer contributions	$ 1.0	$ 1.0