Earnings Per Share - Computation of Basic and Diluted Earnings Per Share for Continuing Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Income (loss) from continuing operations	$ 4,726	$ 9,864	$ 11,416	$ 25,026	$ (565)	$ 10,987	$ 8,387	$ 21,798	$ 51,032	$ 40,607	$ 35,003
Basic
Weighted average common shares outstanding	54,034	54,142	53,968	53,293	53,019	52,648	52,031	51,572	53,862	52,321	50,280
Diluted
Stock options									1,499	870	876
Restricted stock awards									328	261	277
Contingent shares										61	29
Convertible senior subordinated notes											1,231
Diluted weighted average common shares outstanding	55,822	55,827	55,831	55,214	53,019	53,846	53,079	52,745	55,689	53,513	52,693
Basic earnings per share from continuing operations	$ 0.09	$ 0.18	$ 0.21	$ 0.47	$ (0.01)	$ 0.21	$ 0.16	$ 0.42	$ 0.95	$ 0.78	$ 0.70
Diluted earnings per share from continuing operations	$ 0.08	$ 0.18	$ 0.20	$ 0.45	$ (0.01)	$ 0.20	$ 0.16	$ 0.41	$ 0.92	$ 0.76	$ 0.66