Stockholders' Equity - Summary of the Company's Stock Options Activity (Detail) - Stock Options - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Number of Options outstanding, beginning of year (in shares)	1,008	1,103	1,641
Number of Options, Exercised (in shares)	(198)	(95)	(525)
Number of Options, Expired / terminated (in shares)	(6)	0	(13)
Number of Options outstanding, end of year (in shares)	804	1,008	1,103
Number of Options exercisable, end of year (in shares)	775	977	1,072
Number of Options expected to vest, end of year (in shares)	25
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Options outstanding, beginning of year (in dollars per share)	$ 5.40	$ 5.37	$ 5.26
Weighted Average Exercise Price, Exercised (in dollars per share)	6.99	5.02	4.95
Weighted Average Exercise Price, Expired / terminated (in dollars per share)	8.32	0.00	7.27
Weighted Average Exercise Price, Options outstanding, end of year (in dollars per share)	4.99	5.40	5.37
Weighted Average Exercise Price, Options exercisable, end of year (in dollars per share)	5.00	5.42	5.39
Weighted Average Exercise Price, Options expected to vest, end of year (in dollars per share)	$ 4.75