Basis of Presentation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) item shares	Mar. 31, 2016 USD ($) shares
Cash and Cash Equivalents
Number of banks in which the entity has its majority cash balances held in demand deposit accounts | item	1
Supplemental Non-Cash Investing and Financing Activities
Accounts payable | $	$ 21,900	$ 17,000
Taxes Collected from Customers
Excise taxes and Hawaii Public Utility Commission fees | $	$ 2,200	$ 2,200
Denominator used to compute basic and diluted earnings per share
Basic earnings per share - weighted average shares	11,529,046	11,475,834
Effect of dilutive securities:
Employee and director restricted stock units (in shares)		24,474
Diluted earnings per share - weighted average shares	11,529,046	11,500,308
Shares attributable to restricted stock units excluded from computation of weighted average dilutive shares	278,701	135,906
Recently Adopted Accounting Pronouncements
Cumulative effect of adoption of new accounting standard for stock compensation | $	$ 550