Share Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended							3 Months Ended	12 Months Ended	3 Months Ended
	Dec. 31, 2012 OptionPlan	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 2005 Omnibus Stock Plan	Dec. 31, 2012 Stock Options And Restricted Stock Units	Dec. 31, 2011 Stock Options And Restricted Stock Units	Dec. 31, 2010 Stock Options And Restricted Stock Units	Mar. 31, 2012 Stock Option	Dec. 31, 2012 Stock Option	Mar. 31, 2012 Restricted Stock	Dec. 31, 2012 Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share based compensation plan	2
Common stock, shares authorizes				1,800,000
Common stock, shares available for issuance				1,089,814
Exercise period, maximum	5 years 4 months 6 days	5 years 8 months 12 days	5 years 9 months 29 days	10 years
Minimum grant price percentage				100.00%
Recognized Compensation expense					$ 1.6	$ 1.3	$ 1.1
Unrecognized Compensation expense		0.3									3.0
Expected cost recognition weighted average period									1 year 4 months 24 days
Fair value of shares vested	$ 0.2	$ 0.3	$ 0.5
Stock granted	20,633							20,633		83,807
Vesting period									2 years 10 months 24 days