Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator
Numerator for basic and diluted earnings per share - income from continuing operations available to common stockholders	$ 37,991	$ 122,604	$ (6,215)	$ (11,591)	$ 51,259	$ 29,344	$ 8,821	$ 6,979	$ 142,789	$ 96,404	$ 76,586
Denominator
Denominator for basic earnings per share - weighted average shares outstanding (in shares)									50,307	50,159	50,350
Effect of dilutive securities - stock options and other stock units (in shares)									198	219	247
Denominator for diluted earnings per share - adjusted weighted average shares outstanding (in shares)									50,505	50,378	50,597
Earnings per share:
Basic (in dollars per share)	$ 0.75	$ 2.44	$ (0.12)	$ (230)	$ 1.02	$ 0.58	$ 0.18	$ 0.14	$ 2.84	$ 1.92	$ 1.52
Diluted (in dollars per share)	$ 0.75	$ 2.42	$ (0.12)	$ (230)	$ 1.02	$ 0.58	$ 0.18	$ 0.14	$ 2.83	$ 1.91	$ 1.51