CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 247,011	$ 274,319
Accounts receivable, net of allowance for doubtful accounts of $1,499 and $1,734, respectively	39,096	33,598
Prepaid expenses and other current assets	20,011	19,706
Total current assets	306,118	327,623
Property and equipment:
Property and equipment	1,233,756	1,136,470
Accumulated depreciation and amortization	(852,474)	(774,829)
Total property and equipment, net	381,282	361,641
Deferred tax assets	17,616	42,241
Deposits and other assets ($736 and $128 restricted, respectively)	5,572	6,387
Total assets	710,588	737,892
Current liabilities:
Accounts payable	11,592	11,551
Accrued and other current liabilities	47,947	47,149
Installment payment agreement, current portion, net of discount of $337 and $204, respectively	7,816	2,587
Capital lease obligations, current maturities	7,171	6,626
Total current liabilities	74,526	67,913
Senior secured 2022 notes, net of unamortized debt costs of $1,870 and $2,257, respectively and including premium of $382 and $462, respectively	373,512	373,205
Senior unsecured 2021 notes, net of unamortized debt costs of $2,060 and $2,575, respectively	187,165	186,650
Capital lease obligations, net of current maturities	150,333	135,335
Other long term liabilities	27,596	28,043
Total liabilities	813,132	791,146
Commitments and contingencies
Stockholders' equity:
Common stock, $0.001 par value; 75,000,000 shares authorized; 45,960,799 and 45,478,787 shares issued and outstanding, respectively	46	45
Additional paid-in capital	456,696	442,799
Accumulated other comprehensive income	(4,600)	(17,193)
Accumulated deficit	(554,686)	(478,905)
Total stockholders' deficit	(102,544)	(53,254)
Total liabilities and stockholders' equity	$ 710,588	$ 737,892