Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Cash paid during the year:
Interest paid, net of amounts capitalized	$ 3,537	$ 2,492
Non-cash investing activities - capital assets acquired under installment contracts	617
Non-cash financing activities - common shares issued for performance based compensation, net of withholding taxes paid	400
Increase to the beginning and ending reported cash, cash equivalents and restricted cash	3,800
Restricted Cash and Investments [Abstract]
Cash and cash equivalents	10,479		$ 15,821
Restricted cash included in other current assets
Escrow deposits for capacity sales	5,000		5,000
Restricted cash included in other assets
Other	325		325
Total cash, cash equivalents and restricted cash	$ 15,804	$ 24,677	$ 21,146	$ 34,137