Employee Benefit Plans - Amounts Included in Regulatory Asset and Accumulated Other Comprehensive Income/Loss Recognized as Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)	$ (15)	$ (15)	$ (30)	$ (30)
Net loss	67	173	132	344
Recognized from accumulated other comprehensive loss	52	92	102	183
Recognized from regulatory asset	0	66	0	131
Total recognized in net periodic benefit cost	52	158	102	314
Chesapeake Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)	0	0	0	(1)
Net loss	38	57	75	114
Recognized from accumulated other comprehensive loss	38	57	75	113
Total recognized in net periodic benefit cost	38	57	75	113
FPU Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net loss	0	81	0	162
Recognized from accumulated other comprehensive loss	0	15	0	31
Recognized from regulatory asset	0	66	0	131
Total recognized in net periodic benefit cost	0	81	0	162
Chesapeake Pension SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)	5	5	9	10
Net loss	12	16	24	32
Recognized from accumulated other comprehensive loss	17	21	33	42
Total recognized in net periodic benefit cost	17	21	33	42
Chesapeake Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Prior service cost (credit)	(20)	(20)	(39)	(39)
Net loss	17	19	33	36
Recognized from accumulated other comprehensive loss	(3)	(1)	(6)	(3)
Total recognized in net periodic benefit cost	$ (3)	$ (1)	$ (6)	$ (3)