Benefit Plans - Stock Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
$ 10.27-15.14 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, minimum (in dollars per share)	$ 10.27
Range of exercise prices, maximum (in dollars per share)	$ 15.23
Number of options outstanding (in shares) | shares	506,478
Average remaining contractual life	4 years 2 months 18 days
Options Outstanding, weighted average exercise price (in dollars per share)	$ 12.49
Number of options exercisable (in shares) | shares	465,478
Options exercisable, weighted average exercise price (in dollars per share)	$ 12.27
$ 17.43-19.22 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, minimum (in dollars per share)	16.38
Range of exercise prices, maximum (in dollars per share)	$ 18.87
Number of options outstanding (in shares) | shares	578,208
Average remaining contractual life	3 years 10 months 18 days
Options Outstanding, weighted average exercise price (in dollars per share)	$ 17.63
Number of options exercisable (in shares) | shares	355,134
Options exercisable, weighted average exercise price (in dollars per share)	$ 18.05