Employee Benefit Plans - Component of Net Periodic Pension Cost (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019
Components of net periodic cost:
Interest cost	$ 48		$ 63	$ 74
Expected Amortization Of Pre Merger Regulatory Asset	0
Chesapeake Postretirement Plan
Components of net periodic cost:
Interest cost	22		26	39
Amortization of prior service cost	(77)		(77)	(77)
Actuarial (gain) loss	34		24	46
Net periodic pension cost	(21)		(27)	8
Expected Amortization Of Pre Merger Regulatory Asset			0	0
Net periodic postretirement cost	$ (21)		$ (27)	$ 8
Assumptions
Discount rate	2.25%		3.00%	4.00%
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	$ 190		$ 166
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	159		(34)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(470)		(225)
Defined Benefit Plan, Plan Assets, Amount	0		0	$ 0
Defined Benefit Plan, Plan Assets, Contributions by Employer	280		59
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	190		166
Defined Benefit Plan, Plan Assets, Benefits Paid	(470)		(225)
Funded status	(934)		(1,033)
Accrued pension cost	$ (934)		$ (1,033)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.83%		2.25%
FPU Medical Plan
Components of net periodic cost:
Interest cost	$ 24		$ 30	48
Amortization of prior service cost	0		0	0
Actuarial (gain) loss	9		(19)	0
Net periodic pension cost	15		11	48
Amortization of pre-merger regulatory asset	0		6	8
Net periodic postretirement cost	$ 15		$ 17	$ 56
Assumptions
Discount rate	2.50%		3.25%	4.25%
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	$ 29		$ 37
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	71		(181)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(129)		(101)
Defined Benefit Plan, Plan Assets, Amount	0		0	$ 0
Defined Benefit Plan, Plan Assets, Contributions by Employer	100		64
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	29		37
Defined Benefit Plan, Plan Assets, Benefits Paid	(129)		(101)
Funded status	(1,004)		(1,009)
Accrued pension cost	$ (1,004)		$ (1,009)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.51%		2.50%
Chesapeake SERP
Components of net periodic cost:
Interest cost	$ 48		$ 63
Actuarial (gain) loss	28		20	85
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0		0	58
Net periodic postretirement cost	$ 76		$ 83	$ 217
Assumptions
Discount rate	2.25%		3.00%	4.00%
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ (12)		$ 144
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(152)		(152)
Defined Benefit Plan, Plan Assets, Contributions by Employer	152		152
Defined Benefit Plan, Plan Assets, Benefits Paid	(152)		(152)
Funded status	(2,096)		(2,212)
Accrued pension cost	$ (2,096)		$ (2,212)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.50%		2.25%
Chesapeake Pension Plan
Components of net periodic cost:
Interest cost	$ 141	[1]	$ 176	$ 375	[2]
Expected return on assets	(166)	[1]	(157)	(487)	[2]
Actuarial (gain) loss	257	[1]	243	391	[2]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	1,810	[1]	203	1,982	[2]
Net periodic pension cost	2,042	[1]	465	2,261	[2]
Amortization of pre-merger regulatory asset	0	[1]	0	0	[2]
Net periodic postretirement cost	$ 2,042	[1]	$ 465	$ 2,261	[2]
Assumptions
Discount rate	2.25%		3.00%	3.00%
Expected return on plan assets	3.50%		3.50%	6.00%
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ (371)		$ 450
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(32)		(82)
Defined Benefit Plan, Plan Assets, Amount	0		4,609	$ 4,630
Defined Benefit Plan, Plan Assets, Contributions by Employer	1,544		304
Defined Benefit Plan, Plan Assets, Benefits Paid	(32)		(82)
Funded status	0		(1,537)
Accrued pension cost	$ 0		$ (1,537)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.50%		2.25%
FPU Pension Plan
Components of net periodic cost:
Interest cost	$ 1,714		$ 2,085	2,452
Expected return on assets	(3,306)		(2,967)	(2,770)
Actuarial (gain) loss	612		552	505
Net periodic pension cost	(980)		(330)	187
Amortization of pre-merger regulatory asset	0		0	543
Net periodic postretirement cost	$ (980)		$ (330)	$ 730
Assumptions
Discount rate	2.50%		3.25%	4.25%
Expected return on plan assets	6.00%		6.00%	6.50%
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ (1,953)		$ 6,069
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(3,097)		(3,092)
Defined Benefit Plan, Plan Assets, Amount	58,712		55,966	$ 49,703
Defined Benefit Plan, Plan Assets, Contributions by Employer	1,597		2,774
Defined Benefit Plan, Plan Assets, Benefits Paid	(3,097)		(3,092)
Funded status	(8,318)		(14,400)
Accrued pension cost	$ (8,318)		$ (14,400)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.75%		2.50%

[1] (2) As a result of the termination of the Chesapeake Pension Plan in 2021, we recorded $0.6 million as the final settlement expense in our consolidated statement of income which reflected a portion of the pension settlement expense that was deemed not recoverable through the regulatory process.

[2] (1) As a result of annuity purchases and lump sum payments associated with the de-risking of the Chesapeake Pension Plan, the discount rate for Chesapeake Pension Plan was re-measured which triggered settlement accounting expense in the fourth quarter of 2019. We recorded an estimated $0.7 million for the settlement expense in our consolidated statement of income which reflected a portion of the pension settlement expense that was deemed not recoverable through the regulatory process.