Supplemental Financial Information - Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Other current liabilities:
Accrued compensation	$ 1,539	$ 879
Accrued interest	894	875
Accrued losses on equipment contracts	3,127	4,805
Other	1,179	822
Other current liabilities	6,739	7,381	$ 6,406	$ 2,747	$ 2,580
Other long-term liabilities:
Deferred rent	1,021	989
Warranty liabilities	152	62
Deferred revenue, related party	2,000	2,000
Other long-term liabilities	2,838	1,401
Other long-term liabilities	$ 6,011	$ 4,452	$ 4,440	$ 4,372	$ 4,280