Schedule of Calculation of Numerator and Denominator in Earnings Per Share (Detail) - Entity [Domain] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 65,303	$ 55,732	$ 122,580	$ 107,470
Weighted average shares and assumed conversions	117,812	117,196	117,790	117,079
BASIC EARNINGS PER SHARE	$ 0.56	$ 0.48	$ 1.05	$ 0.93
DILUTED EARNINGS PER SHARE	$ 0.55	$ 0.48	$ 1.04	$ 0.92
Basic Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 65,303	$ 55,732	$ 122,580	$ 107,470
Weighted average common shares outstanding, basic	116,962	116,114	116,799	115,944
Diluted Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 65,303	$ 55,732	$ 122,580	$ 107,470
Weighted average common shares outstanding, diluted	116,962	116,114	116,799	115,944
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	720	835	794	899
Restricted stock based compensation
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	130	247	197	236