Employee Benefit Plans (Detail) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2021		Jun. 30, 2020		Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost		$ (19)		$ (19)		$ (38)	$ (38)
Defined Benefit Plan Actuarial Gain Loss, Net Settlement				198			396
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		230		217		458	434
Defined Benefit Plan Amounts Recognized Gain (Loss)		211		198		420	396
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	87		89		171	178
Defined Benefit Plan Amounts Recognized From Regulatory Asset		124		109		249	218
Defined Benefit Plan, Expected Future Benefit Payment, Remainder of Fiscal Year		700				700
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		100
Interest cost		34		46		68	92
Expected return on plan assets		(40)		(42)		(80)	(84)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		60		65		120	130
Net periodic cost (benefit)		54	[1]	69	[1]	108	138
Total periodic cost		54		69		108	138
Defined Benefit Plan Amounts Recognized Gain (Loss)		60		65		120	130
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	60		65		120	130
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		300				300
Florida Public Utilities Company Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		500
Interest cost		429		518		858	1,036
Expected return on plan assets		(830)		(745)		(1,660)	(1,490)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		155		135		310	270
Net periodic cost (benefit)		(246)	[1]	(92)	[1]	(492)	(184)
Amortization of pre-merger regulatory asset		0		0		0	0
Total periodic cost		(246)		(92)		(492)	(184)
Defined Benefit Plan Amounts Recognized Gain (Loss)		155		135		310	270
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	29		26		58	52
Defined Benefit Plan Amounts Recognized From Regulatory Asset		126		109		252	218
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		2,100				2,100
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer						100
Interest cost		12		16		24	32
Defined Benefit Plan Actuarial Gain Loss, Net Settlement				5			10
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		7		5		14	10
Net periodic cost (benefit)		19	[1]	21	[1]	38	42
Total periodic cost		19		21		38	42
Defined Benefit Plan Amounts Recognized Gain (Loss)		7		5		14	10
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	7		5		14	10
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		200				200
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer						200
Interest cost		6		8		12	16
Amortization of prior service cost		(19)		(19)		(38)	(38)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		10		12		18	24
Net periodic cost (benefit)		(3)	[1]	1	[1]	(8)	2
Total periodic cost		(3)		1		(8)	2
Defined Benefit Plan Amounts Recognized Gain (Loss)		(9)		(7)		(20)	(14)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]	(9)		(7)		(20)	(14)
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		200				200
Florida Public Utilities Company Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost		6		10		12	20
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		(2)				(4)
Net periodic cost (benefit)		4	[1]	10	[1]	8	20
Amortization of pre-merger regulatory asset		0		2		0	4
Total periodic cost		4		$ 12		8	$ 24
Defined Benefit Plan Amounts Recognized Gain (Loss)		(2)				(4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[1]					(1)
Defined Benefit Plan Amounts Recognized From Regulatory Asset		(2)				(3)
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		$ 100				$ 100

[1] See Note 9, Stockholders' Equity.