Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
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	$ 26.1	$ 20.6	$ 21.2
Summary of Significant Accounting Policies
Advance billing period for basic local service and enhanced calling feature services	1 month
Taxes Collected from Customers
Excise taxes and Hawaii Public Utility Commission fees	$ 8.4	$ 8.2	$ 7.5
Maximum
Recently Adopted Accounting Pronouncements
Period of IRU related payments to be received	25 years