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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income, Basic	$ 40,994	$ 41,178	$ 117,968	$ 136,700
Net income, Diluted	$ 40,994	$ 41,178	$ 117,968	$ 136,700
Weighted average common shares outstanding, Basic	118,597	118,182	118,544	118,044
Weighted average common shares outstanding, Basic	118,597	118,182	118,544	118,044
Weighted average shares and assumed conversions	118,849	118,528	118,711	118,459
BASIC EARNINGS PER SHARE	$ 0.35	$ 0.35	$ 1.00	$ 1.16
DILUTED EARNINGS PER SHARE	$ 0.34	$ 0.35	$ 0.99	$ 1.15
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	178	262	123	353
Restricted stock based awards
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities	74	84	44	62