Commitments and Contingencies - Trans-Pacific Submarine Cable and CAF (Details) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) location	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Aug. 31, 2014 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
CAF annual funding	$ 4.4
Period of support service		6 years
Number of eligible locations to offer broadband | location		11,000
Number of locations for interim deployment obligation | location		4,400
Number of locations deployed | location		5,452
Revenue recognized from CAF first year funds		$ 4.4	$ 4.4	$ 3.3
Jointly owned utility plant
Jointly Owned Utility Plant Interests [Line Items]
Cost of construction					$ 235.0
Company investment in construction costs of plant					$ 25.0
Paid to the cable contractor for the cable build		$ 25.1
Period of up-front payment received		25 years
Proceeds from sale of capacity		$ 30.2
Escrow deposit		$ 5.0
Minimum
Jointly Owned Utility Plant Interests [Line Items]
Downstream broadband service data transfer rate (Mbps)		10
Upstream broadband service data transfer rate (Mbps)		1