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, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		$ (524)
Net loss		23,467
Total		22,943
Accumulated other comprehensive loss pre-tax		7,986
Post-merger regulatory asset		14,957
Subtotal		22,943
Pre-merger regulatory asset		557
Total unrecognized cost		23,500
Chesapeake Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		0
Net loss		3,865
Total		3,865
Accumulated other comprehensive loss pre-tax	[1]	3,865
Post-merger regulatory asset		0
Subtotal		3,865
Pre-merger regulatory asset		0
Total unrecognized cost		3,865
FPU Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		0
Net loss		18,544
Total		18,544
Accumulated other comprehensive loss pre-tax	[1]	3,523
Post-merger regulatory asset		15,021
Subtotal		18,544
Pre-merger regulatory asset		543
Total unrecognized cost		19,087
Chesapeake SERP
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		0
Net loss		559
Total		559
Accumulated other comprehensive loss pre-tax	[1]	559
Post-merger regulatory asset		0
Subtotal		559
Pre-merger regulatory asset		0
Total unrecognized cost		559
Chesapeake Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		(524)
Net loss		578
Total		54
Accumulated other comprehensive loss pre-tax	[1]	54
Post-merger regulatory asset		0
Subtotal		54
Pre-merger regulatory asset		0
Total unrecognized cost		54
FPU Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		0
Net loss		(79)
Total		(79)
Accumulated other comprehensive loss pre-tax	[1]	(15)
Post-merger regulatory asset		(64)
Subtotal		(79)
Pre-merger regulatory asset		14	$ 22
Total unrecognized cost		$ (65)

[1] The total amount of accumulated other comprehensive loss recorded on our consolidated balance sheet as of December 31, 2018 is net of income tax benefits of $2.1 million.