Employee Benefit Plans - Schedule of Funded Status of Benefit Obligation and Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in benefit obligation:
Interest cost	$ 0.1	$ 0.1	$ 0.1
FPU Pension Plan
Change in benefit obligation:
Benefit obligation - beginning of year	49.7	49.9
Interest cost	2.4	2.5	1.8
Actuarial loss	(2.0)	0.5
Benefits paid	(4.6)	(3.2)
Benefit obligation - end of year	45.5	49.7	49.9
Change in plan assets:
Balance, beginning of year	49.5	46.2
Actual return on plan assets	4.2	6.5
Employer contributions	0.0	0.0
Benefits paid	(4.6)	(3.2)
Balance, end of year	49.1	49.5	$ 46.2
Reconciliation:
Accrued pension cost	$ 3.6	$ (0.2)
Assumptions:
Discount rate	5.50%	5.00%
Expected return on plan assets	6.00%	6.00%	6.00%
Chesapeake SERP
Change in benefit obligation:
Benefit obligation - beginning of year	$ 1.6	$ 1.7
Interest cost	0.1	0.1
Actuarial loss	0.0	0.0
Benefits paid	(0.2)	(0.2)
Benefit obligation - end of year	1.5	1.6	$ 1.7
Change in plan assets:
Employer contributions	0.2	0.2
Benefits paid	(0.2)	(0.2)
Reconciliation:
Accrued pension cost	$ (1.5)	$ (1.6)
Assumptions:
Discount rate	5.40%	4.88%
Chesapeake Postretirement Plan
Reconciliation:
Funded status	$ (0.9)	$ (1.1)
FPU Medical Plan
Reconciliation:
Funded status	$ (0.3)	$ (0.4)