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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 50,676	$ 57,546	$ 173,256	$ 165,016
Weighted average shares and assumed conversions	117,774	117,389	117,786	117,183
BASIC EARNINGS PER SHARE	$ 0.43	$ 0.50	$ 1.48	$ 1.42
DILUTED EARNINGS PER SHARE	$ 0.43	$ 0.49	$ 1.47	$ 1.41
Basic Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 50,676	$ 57,546	$ 173,256	$ 165,016
Weighted average common shares outstanding, basic	117,066	116,185	116,889	116,025
Diluted Earnings Per Share
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 50,676	$ 57,546	$ 173,256	$ 165,016
Weighted average common shares outstanding, diluted	117,066	116,185	116,889	116,025
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	559	886	716	895
Restricted stock based compensation
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	149	318	181	263