Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, shares	484,794
Options outstanding, weighted average exercise price	$ 13.26
Options outstanding, weighted average remaining contractual life (in years)	1 year 10 months 4 days
Options vested and exercisable, shares	484,794
Options vested and exercisable, weighted average exercise Price	$ 13.26
Options vested and exercisable, weighted average remaining contractual life (in years)	1 year 10 months 4 days
$ 9.00 to $ 12.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower limit	$ 9.00
Exercise Price, Upper limit	$ 12.00
Options outstanding, shares	197,980
Options outstanding, weighted average exercise price	$ 10.85
Options outstanding, weighted average remaining contractual life (in years)	11 months 3 days
Options vested and exercisable, shares	197,980
Options vested and exercisable, weighted average exercise Price	$ 10.85
Options vested and exercisable, weighted average remaining contractual life (in years)	11 months 3 days
$12.01 to $15.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower limit	$ 12.01
Exercise Price, Upper limit	$ 15.00
Options outstanding, shares	184,126
Options outstanding, weighted average exercise price	$ 14.63
Options outstanding, weighted average remaining contractual life (in years)	2 years 1 month 16 days
Options vested and exercisable, shares	184,126
Options vested and exercisable, weighted average exercise Price	$ 14.63
Options vested and exercisable, weighted average remaining contractual life (in years)	2 years 1 month 16 days
$15.01 to $17.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price, Lower limit	$ 15.01
Exercise Price, Upper limit	$ 17.00
Options outstanding, shares	102,688
Options outstanding, weighted average exercise price	$ 15.45
Options outstanding, weighted average remaining contractual life (in years)	3 years 1 month 12 days
Options vested and exercisable, shares	102,688
Options vested and exercisable, weighted average exercise Price	$ 15.45
Options vested and exercisable, weighted average remaining contractual life (in years)	3 years 1 month 12 days