Schedule of Calculation of Numerator and Denominator in 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
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income, Basic	$ 39,197	$ 45,475	$ 76,974	$ 95,522
Net income, Diluted	$ 39,197	$ 45,475	$ 76,974	$ 95,522
Weighted average common shares outstanding, Basic	118,546	118,164	118,501	117,974
Weighted average common shares outstanding, Basic	118,546	118,164	118,501	117,974
Weighted average shares and assumed conversions	118,648	118,585	118,626	118,423
BASIC EARNINGS PER SHARE	$ 0.33	$ 0.38	$ 0.65	$ 0.81
DILUTED EARNINGS PER SHARE	$ 0.33	$ 0.38	$ 0.65	$ 0.81
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	92	377	96	398
Restricted stock based awards
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	10	44	29	51