Schedule of Calculation of Numerator and Denominator in Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income, Basic									$ 219,919	$ 221,854	$ 195,022
Net income, Diluted									$ 219,919	$ 221,854	$ 195,022
Weighted average common shares outstanding, Basic									117,384	116,949	116,109
Weighted average common shares outstanding, Basic									117,384	116,949	116,109
Weighted average shares and assumed conversions									117,791	117,785	117,312
BASIC EARNINGS PER SHARE	$ 0.52	$ 0.47	$ 0.49	$ 0.39	$ 0.41	$ 0.43	$ 0.56	$ 0.49	$ 1.87	$ 1.90	$ 1.68
DILUTED EARNINGS PER SHARE	$ 0.52	$ 0.47	$ 0.49	$ 0.39	$ 0.41	$ 0.43	$ 0.55	$ 0.49	$ 1.87	$ 1.88	$ 1.66
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities									306	631	895
Restricted stock based awards
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities									101	205	308