Employee Benefit Plans - Employee Benefit Plans (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 Plan Disclosure [Line Items]
Document Period End Date			Jun. 30, 2014
Amortization of prior service cost	$ (15)	$ (15)	$ (30)	$ (30)
Amortization of net loss	67	173	132	344
Chesapeake Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	106	103	213	205
Expected return on plan assets	(132)	(126)	(265)	(252)
Amortization of prior service cost	0	0	0	(1)
Amortization of net loss	38	57	75	114
Net periodic cost (benefit)	12	34	23	66
Total periodic cost	12	34	23	66
FPU Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	647	594	1,294	1,188
Expected return on plan assets	(772)	(718)	(1,545)	(1,437)
Amortization of net loss	0	81	0	162
Net periodic cost (benefit)	(125)	(43)	(251)	(87)
Amortization of pre-merger regulatory asset	191	191	381	381
Total periodic cost	66	148	130	294
Chesapeake Pension SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	23	20	46	41
Amortization of prior service cost	5	5	9	10
Amortization of net loss	12	16	24	32
Net periodic cost (benefit)	40	41	79	83
Total periodic cost	40	41	79	83
Chesapeake Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	13	12	26	24
Amortization of prior service cost	(20)	(20)	(39)	(39)
Amortization of net loss	17	19	33	36
Net periodic cost (benefit)	10	11	20	21
Total periodic cost	10	11	20	21
FPU Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	16	16	33	32
Amortization of net loss	0	0	0	0
Net periodic cost (benefit)	16	16	33	32
Amortization of pre-merger regulatory asset	2	2	4	4
Total periodic cost	$ 18	$ 18	$ 37	$ 36