Employee Benefit Plans - Additional Information (Detail) (USD $)	9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2013 Chesapeake Pension Plan [Member]	Sep. 30, 2013 Chesapeake Pension Plan [Member]	Sep. 30, 2013 Chesapeake Pension Plan [Member]	Dec. 31, 2012 Chesapeake Pension Plan [Member]	Sep. 30, 2013 FPU Pension Plan [Member]	Sep. 30, 2013 FPU Pension Plan [Member]	Dec. 31, 2013 FPU Pension Plan [Member]	Sep. 30, 2013 Chesapeake Pension SERP [Member]	Sep. 30, 2013 Chesapeake Pension SERP [Member]	Dec. 31, 2013 Chesapeake Pension SERP [Member]	Sep. 30, 2013 Chesapeake Postretirement Plan [Member]	Sep. 30, 2013 Chesapeake Postretirement Plan [Member]	Dec. 31, 2013 Chesapeake Postretirement Plan [Member]	Sep. 30, 2013 FPU Medical Plan [Member]	Sep. 30, 2013 FPU Medical Plan [Member]	Dec. 31, 2013 FPU Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected pension and postretirement benefit costs	$ 999,000
Expected amortization of pre merger regulatory asset	769,000
Unamortized balance of regulatory asset			4,600,000	4,600,000	5,200,000
Contribution to pension plan			142,000	233,000		211,000	421,000		22,000	67,000		16,000	53,000		50,000	91,000
Additional contribution to pension plan		$ 364,000						$ 842,000			$ 88,000			$ 97,000			$ 258,000