Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator
Numerator for basic and diluted earnings per share - Net income attributable to common stockholders	$ 15,008	$ 45,310	$ 23,292	$ 75,872
Denominator
Denominator for basic earnings per share - weighted average shares outstanding (in shares)	50,436	52,796	50,636	52,815
Effect of dilutive securities - stock options and other stock units (in shares)	154	395	247	542
Denominator for diluted earnings per share - adjusted weighted average shares outstanding (in shares)	50,590	53,191	50,883	53,357
Earnings per share:
Basic (in dollars per share)	$ 0.30	$ 0.86	$ 0.46	$ 1.44
Diluted (in dollars per share)	$ 0.30	$ 0.85	$ 0.46	$ 1.42