Stock Option Awards (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Stock Options [Line Items]
Number of options Outstanding	1,902,267	2,343,000	3,427,000	4,322,000
Weighted-average exercise price, outstanding	$ 13.95	$ 14.24	$ 14.35	$ 14.28
Number of options exercisable	1,431,288	1,282,000	1,393,000	1,025,000
Weighted-average exercise price, exercisable	$ 13.98	$ 14.52	$ 14.97	$ 15.52
$12.50 to $14.78 [Member]
Schedule Of Stock Options [Line Items]
Range of exercise prices, lower limit	12.50
Range of exercise prices, upper limit	$ 14.78
Number of options Outstanding	1,727,810
Weighted-average exercise price, outstanding	$ 13.77
Number of options exercisable	1,289,044
Weighted-average exercise price, exercisable	$ 13.76
$14.94 to $16.80 [Member]
Schedule Of Stock Options [Line Items]
Range of exercise prices, lower limit	14.94
Range of exercise prices, upper limit	$ 16.80
Number of options Outstanding	158,517
Weighted-average exercise price, outstanding	$ 15.51
Number of options exercisable	126,304
Weighted-average exercise price, exercisable	$ 15.58
$18.45 to $18.74 [Member]
Schedule Of Stock Options [Line Items]
Range of exercise prices, lower limit	18.45
Range of exercise prices, upper limit	$ 18.74
Number of options Outstanding	15,940
Weighted-average exercise price, outstanding	$ 18.70
Number of options exercisable	15,940
Weighted-average exercise price, exercisable	$ 18.70