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, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost		$ 74	$ 83	$ 89
Prior service cost (credit)		(447)
Net loss		22,727
Total		22,280
Accumulated other comprehensive loss pre-tax		6,641
Post-merger regulatory asset		15,639
Subtotal		22,280
Pre-merger regulatory asset		6
Total unrecognized cost		22,286
Chesapeake Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost		375	384	402
Prior service cost (credit)		0
Net loss		2,241
Total		2,241
Accumulated other comprehensive loss pre-tax	[1]	2,241
Post-merger regulatory asset		0
Subtotal		2,241
Pre-merger regulatory asset		0
Total unrecognized cost		2,241
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		487	542	495
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(391)	(343)	(399)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		(1,982)	0	0
Net Periodic Cost Benefit		2,261	185	306
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		2,261	185	306
Amortization Of Pre Merger Regulatory Asset		$ 0	$ 0	$ 0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		3.00%	3.50%	3.75%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		6.00%	6.00%	6.00%
FPU Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost		$ 2,452	$ 2,339	$ 2,482
Prior service cost (credit)		0
Net loss		19,339
Total		19,339
Accumulated other comprehensive loss pre-tax	[1]	3,674
Post-merger regulatory asset		15,665
Subtotal		19,339
Pre-merger regulatory asset		0
Total unrecognized cost		19,339
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		2,770	3,091	2,779
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(505)	(404)	(513)
Net Periodic Cost Benefit		187	(348)	216
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		730	413	977
Amortization Of Pre Merger Regulatory Asset		$ 543	$ 761	$ 761
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		4.25%	3.75%	4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		6.50%	6.50%	6.50%
Chesapeake SERP
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost		$ 74	$ 83
Prior service cost (credit)		0
Net loss		575
Total		575
Accumulated other comprehensive loss pre-tax	[1]	575
Post-merger regulatory asset		0
Subtotal		575
Pre-merger regulatory asset		0
Total unrecognized cost		575
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(85)	(101)	$ (87)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		(58)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 217	$ 184	$ 176
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		4.00%	3.50%	3.75%
Chesapeake Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost		$ 39	$ 38	$ 41
Prior service cost (credit)		(447)
Net loss		604
Total		157
Accumulated other comprehensive loss pre-tax	[1]	157
Post-merger regulatory asset		0
Subtotal		157
Pre-merger regulatory asset		0
Total unrecognized cost		157
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		(46)	(58)	(53)
Net Periodic Cost Benefit		8	19	17
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 8	$ 19	$ 17
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		4.00%	3.50%	3.75%
FPU Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost		$ 48	$ 47	$ 50
Prior service cost (credit)		0
Net loss		(32)
Total		(32)
Accumulated other comprehensive loss pre-tax	[1]	(6)
Post-merger regulatory asset		(26)
Subtotal		(32)
Pre-merger regulatory asset		6
Total unrecognized cost		(26)
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year		0	0	0
Net Periodic Cost Benefit		48	47	50
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		56	55	58
Amortization Of Pre Merger Regulatory Asset		$ 8	$ 8	$ 8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		4.25%	3.75%	4.00%

[1] The total amount of accumulated other comprehensive loss recorded on our consolidated balance sheet as of December 31, 2019 is net of income tax benefits of $1.7 million.