CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 1,499	$ 1,734
Deposits and other assets, restricted (in dollars)	736	128
Liabilities and stockholders' equity
Installment payment agreement, discount	$ 337	$ 204
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	45,960,799	45,478,787
Common stock, shares outstanding	45,960,799	45,478,787
Senior secured 2022 notes
Liabilities and stockholders' equity
Unamortized debt costs	$ 1,870	$ 2,257
Unamortized debt premium	382	462
Senior unsecured 2021 notes
Liabilities and stockholders' equity
Unamortized debt costs	$ 2,060	$ 2,575