Employee Benefit Plans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Document Period End Date			Sep. 30, 2014
Expected pension and postretirement benefit costs			$ 578,000
Expected amortization of pre merger regulatory asset			769,000
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Unamortized balance of regulatory asset	3,800,000		3,800,000		4,400,000
Defined Benefit Plan, Net Periodic Benefit Cost	11,000	33,000	34,000	99,000
Contribution to pension plan	308,000		529,000
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year			709,000
Consolidated [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost			191,000
FPU Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost	(126,000)	(44,000)	(377,000)	(131,000)
Contribution to pension plan	1,383,000		2,013,000
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year			2,641,000
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost	40,000	42,000	119,000	124,000
Contribution to pension plan	22,000		67,000
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year			88,000
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost	10,000	11,000	31,000	33,000
Contribution to pension plan	12,000		57,000
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year			95,000
FPU Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost	17,000	16,000	50,000	47,000
Contribution to pension plan	43,000		187,000
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year			$ 245,000