Deferred Tax Assets and Liabilities, Non Current (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Schedule of Deferred Tax Assets and Liabilities [Line Items]
Utility Plant Differences	$ 102,479,000	$ 66,907,000
Net Operating Loss Carryforwards	(17,403,000)	(8,521,000)
AMT Tax Credit Carryforwards	(1,538,000)	(1,538,000)
Regulatory Assets & Liabilities	17,174,000	17,872,000
Retirement Benefit Obligations	(28,287,000)	(38,644,000)
Other, net	754,000	2,606,000
Total Noncurrent Deferred Income Tax Liabilities	$ 73,200,000	$ 38,700,000