Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Aircraft	$ 19,160	$ 19,063
Equipment	19,788	20,044
Furniture and fixtures	7,201	7,248
Leasehold improvements	21,612	21,945
Property, plant and equipment, gross	67,761	68,300
Accumulated depreciation and amortization	(58,997)	(58,517)
Total property and equipment, net	$ 8,764	$ 9,783