Employee Benefit Plans - Schedule of Amounts Not Yet Reflected in Net Periodic Benefit Cost and Included in Accumulated Other Comprehensive Income Loss or Regulatory Assets (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 48		$ 63	$ 74
Prior service cost (credit)		(293)
Net loss		18,953
Total		18,660
Accumulated other comprehensive loss pre-tax		4,385
Post-merger regulatory asset		(14,275)
Total unrecognized cost		(18,660)
Chesapeake Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		141	[1]	176	375	[2]
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		166	[1]	157	487	[2]
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(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 Cost Benefit		2,042	[1]	465	2,261	[2]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		2,042	[1]	465	2,261	[2]
Amortization Of Pre Merger Regulatory Asset		$ 0	[1]	$ 0	$ 0	[2]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		2.25%		3.00%	3.00%
Expected return on plan assets		3.50%		3.50%	6.00%
FPU Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 1,714		$ 2,085	$ 2,452
Prior service cost (credit)		0
Net loss		17,737
Total		17,737
Accumulated other comprehensive loss pre-tax	[3]	3,370
Post-merger regulatory asset		(14,367)
Total unrecognized cost		(17,737)
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		3,306		2,967	2,770
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(612)		(552)	(505)
Net Periodic Cost Benefit		(980)		(330)	187
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		(980)		(330)	730
Amortization Of Pre Merger Regulatory Asset		$ 0		$ 0	$ 543
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		2.50%		3.25%	4.25%
Expected return on plan assets		6.00%		6.00%	6.50%
Chesapeake SERP
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 48		$ 63
Prior service cost (credit)		0
Net loss		659
Total		659
Accumulated other comprehensive loss pre-tax	[3]	659
Post-merger regulatory asset		0
Total unrecognized cost		(659)
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(28)		(20)	$ (85)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		0		0	(58)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 76		$ 83	$ 217
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		2.25%		3.00%	4.00%
Chesapeake Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 22		$ 26	$ 39
Prior service cost (credit)		(293)
Net loss		671
Total		378
Accumulated other comprehensive loss pre-tax	[3]	378
Post-merger regulatory asset		0
Total unrecognized cost		(378)
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(34)		(24)	(46)
Net Periodic Cost Benefit		(21)		(27)	8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ (21)		$ (27)	$ 8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		2.25%		3.00%	4.00%
FPU Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 24		$ 30	$ 48
Prior service cost (credit)		0
Net loss		(114)
Total		(114)
Accumulated other comprehensive loss pre-tax	[3]	(22)
Post-merger regulatory asset		(92)
Total unrecognized cost		(114)
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(9)		19	0
Net Periodic Cost Benefit		15		11	48
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		15		17	56
Amortization Of Pre Merger Regulatory Asset		$ 0		$ 6	$ 8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		2.50%		3.25%	4.25%

[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.

[3] The total amount of accumulated other comprehensive loss recorded on our consolidated balance sheet as of December 31, 2021 is net of income tax benefits of $1.1 million.