Income Tax - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Allowance for doubtful accounts	$ 195	$ 265
Unearned income	3,136	2,023
Investment in equity subsidiary	447	385
Alternative minimum tax	51	176
Share-based compensation	1,208	697
Debt Issuance Costs	69	127
General Reserves	505	474
Derivative Liability	0	172
Accrual of contract maintenance cost	472	0
Impairment of asset	425	0
Other temporary assets	1,754	704
Total gross deferred tax assets	8,262	5,023
Deferred tax liabilities
Deferred compensation	1,617	1,458
Difference between the assigned values and the tax basis of assets and liabilities recognized in purchase	19,124	17,738
Other temporary liabilities	353	0
Total gross deferred tax liabilities	21,094	19,196
Deferred tax liability, net	$ (12,832)	$ (14,173)