Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income	$ 1,599	$ 1,432
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	44,443	43,221
Deferred financing amortization	1,005	953
Employee retirement benefits	(3,896)	(3,565)
Provision for uncollectible receivables	2,139	1,634
Stock based compensation	1,141	900
Deferred income taxes	1,377	1,621
Changes in operating assets and liabilities:
Receivables	1,477	(3,025)
Material and supplies	(104)	(92)
Prepaid expenses and other current assets	(2,594)	(1,944)
Accounts payable and accrued expenses	6,837	(2,037)
Advance billings and customer deposits	(1,593)	668
Other current liabilities	(385)	(465)
Other	(157)	492
Net cash provided by operating activities	51,289	39,793
Cash flows from investing activities:
Capital expenditures	(52,898)	(52,916)
Funds released from restricted cash account		400
Net cash used in investing activities	(52,898)	(52,516)
Cash flows from financing activities:
Proceeds from exercise of warrant		3,341
Proceeds from installment financing	1,698	2,279
Repayment of capital lease and installment financing	(1,707)	(1,976)
Repayment of debt	(1,500)	(1,500)
Refinancing and loan amendment costs	(688)	(150)
Taxes paid related to net share settlement of equity awards	(351)	(928)
Net cash used in financing activities	(2,548)	1,066
Net change in cash and cash equivalents	(4,157)	(11,657)
Cash and cash equivalents, beginning of period	30,312	39,885
Cash and cash equivalents, end of period	26,155	28,228
Supplemental disclosure of cash flow information:
Interest paid, net of amounts capitalized	$ 6,350	$ 7,604