Organization and Principles of Consolidation (Details) mi in Thousands	Mar. 31, 2017 state subscription mi
Product Information [Line Items]
Number of operating states | state	17
Communication Services
Product Information [Line Items]
Number of route miles in fiber network | mi	22
Number of data subscribers	305,400
Communication Services | Maine, New Hampshire and Vermont
Product Information [Line Items]
Number of route miles in fiber network | mi	18
Ethernet Circuits
Product Information [Line Items]
Number of data subscribers	16,000
Residential Voice Lines
Product Information [Line Items]
Number of data subscribers	356,100