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Employee Benefit Plans - Amounts Included in Regulatory Asset and Accumulated Other Comprehensive Income/Loss Recognized as Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Prior service cost (credit) |  | $ (19) | $ (19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) |  | 237 | 276
Recognized from accumulated other comprehensive loss | [1] | 130 | 151
Recognized from regulatory asset |  | 88 | 106
Total recognized in net periodic benefit cost |  | 218 | 257
Chesapeake Pension Plan [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) |  | 88 | 107
Recognized from accumulated other comprehensive loss | [1] | 88 | 107
Total recognized in net periodic benefit cost |  | 88 | 107
Florida Public Utilities Company Pension Plan [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) |  | 109 | 131
Recognized from accumulated other comprehensive loss | [1] | 21 | 25
Recognized from regulatory asset |  | 88 | 106
Total recognized in net periodic benefit cost |  | 109 | 131
Chesapeake Pension SERP [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) |  | 25 | 22
Recognized from accumulated other comprehensive loss | [1] | 25 | 22
Total recognized in net periodic benefit cost |  | 25 | 22
Chesapeake Postretirement Plan [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Prior service cost (credit) |  | (19) | (19)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) |  | 15 | 16
Recognized from accumulated other comprehensive loss | [1] | (4) | (3)
Total recognized in net periodic benefit cost |  | $ (4) | $ (3)
[1] | See Note 8, Stockholder's Equity.

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- Definition Defined Benefit Plan Amounts Recognized From Regulatory Asset + References No definition available. + Details
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- Definition Defined Benefit Plan Amounts Recognized Gain (Loss) + References No definition available. + Details
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- Definition Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] + References No definition available. + Details
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- Definition Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580 + Details
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