Computation of Earnings Per Share (Detail) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share Basic And Diluted [Line Items]
Basic earnings per share, Weighted Average Shares	83,936	83,730	83,922	83,704
Potential dilutive effect of restricted stock options outstanding, Weighted Average Shares	199	186	209	226
Diluted earnings per share, Weighted Average Shares	84,135	83,916	84,131	83,930
Basic earnings per share, Earnings per Share	$ 0.72	$ 0.71	$ 1.20	$ 1.40
Potential dilutive effect of restricted stock options outstanding, Earnings per Share	0	0	0	0
Diluted earnings per share, Earnings per Share	$ 0.72	$ 0.71	$ 1.20	$ 1.40