Summary of Activity under Stock-Based Compensation Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Stock Options Number Outstanding
Beginning Balance	832,941
Granted	0
Cancelled or Expired	(160,500)
Exercised	0	0
Ending Balance	672,441	832,941
Vested or expected to vest at December 31, 2017	661,204
Exercisable at December 31, 2017	467,003
Stock Options Average Exercise Price per share
Beginning Balance	$ 7.11
Cancelled or Expired	10.58
Ending Balance	6.28	$ 7.11
Vested or expected to vest at December 31, 2017	6.31
Exercisable at December 31, 2017	$ 6.99
Stock Options Remaining Contractual Life (in years)
Remaining Contractual Life	7 years 5 months 23 days
Vested or expected to vest at December 31, 2017	7 years 5 months 16 days
Exercisable at December 31, 2017	7 years 1 month 9 days