Inventories - Summary of inventories (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw material and common parts, net of reserve	$ 6,490		$ 6,680
Work-in-process, net of reserve	2,889		2,280
Finished goods, net of reserve	2,726		3,080
Total inventories	$ 12,105	[1]	$ 12,040

[1] Unaudited