Equity Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	$ 0.2	$ 0.4	$ 0.7	$ 0.8
Cash received from exercise of stock option	0.3		0.9
Number of options exercised, intrinsic value	0.1		0.6	0.2
Tax Benefit From Stock Options			0.2	0.1
Number of options granted	12,500	0	12,500	0
Stock Option Plan 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options and restricted shares authorized	1,750,000		1,750,000
Additional shares authorized under the plan			1,200,000
Performance Based Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	7,500		84,790
Restricted shares Vested			61,800
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	1.8		1.8
Weighted average expected amortization period			2 years 4 months 24 days
Unvested restricted stock awards	326,940		326,940
Time Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted			5,000
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	$ 1.4		$ 1.4
Weighted average expected amortization period			2 years 10 months 24 days
Exercised	27,337		97,986