Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accrued liabilities
Accrued payroll and other compensation	$ 6,029	$ 6,254
Accrued state sales taxes	4,294	3,881
Accrued vendor charges	1,054	713
Other	4,517	2,411
Total accrued liabilities	$ 15,894	$ 13,259