Shareholders' Equity - Summary of Stock Option (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May 16, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Beginning balance of outstanding shares		1,519,000	1,877,000	1,727,000
Granted, Shares	0	128,000	105,000	286,000
Forfeitures, Shares		(700,000)	(268,000)	(106,000)
Exercised, Shares		(292,000)	(195,000)	(30,000)
Ending balance of outstanding, shares		655,000	1,519,000	1,877,000	1,727,000
Exercisable, Shares		463,000	959,000	977,000
Beginning Balance of Outstanding Weighted Average Exercise Price		$ 10.25	$ 10.30	$ 10.12
Granted, Weighted Average Exercise Price		9.24	7.36	11.55
Forfeitures, Weighted Average Exercise Price		12.44	11.91	12.31
Exercised, Weighted Average Exercise Price		3.92	6.90	4.47
Ending Balance of Outstanding Weighted Average Exercise Price		10.53	10.25	10.30	$ 10.12
Exercisable, Weighted Average Exercise Price		$ 10.49	$ 9.23	$ 8.48
Outstanding, Weighted Average Remaining Contractual Term		6 years	6 years 1 month 6 days	6 years 9 months 18 days	7 years 3 months 18 days
Exercisable, Weighted Average Remaining Contractual Term		5 years 2 months 12 days	5 years 3 months 18 days	5 years 4 months 24 days
Outstanding, Aggregate Intrinsic Value		$ 78	$ 5,816	$ 1,769
Exercisable, Aggregate Intrinsic Value		$ 78	$ 4,608	$ 1,765