Schedule of Calculation of Numerator and Denominator in Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income, Basic	$ 41,178	$ 55,340	$ 136,700	$ 159,230
Net income, Diluted	$ 41,178	$ 55,340	$ 136,700	$ 159,230
Weighted average common shares outstanding, Basic	118,182	117,443	118,044	117,360
Weighted average common shares outstanding, Basic	118,182	117,443	118,044	117,360
Weighted average shares and assumed conversions	118,528	117,694	118,459	117,824
BASIC EARNINGS PER SHARE	$ 0.35	$ 0.47	$ 1.16	$ 1.36
DILUTED EARNINGS PER SHARE	$ 0.35	$ 0.47	$ 1.15	$ 1.35
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	262	207	353	384
Restricted stock based awards
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	84	44	62	80