Equity Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	$ 0.7	$ 0.2	$ 1.3	$ 0.7
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	12,500	0	12,500
Cash received from exercise of stock option	0.4	0.3	0.8	0.9
Number of options exercised, intrinsic value	0.8	0.1	1.3	0.6
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	0.3		0.5	0.2
Stock Option Plan 2012 [Member]
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
Time Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	0		28,769	5,000
Performance Based Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted			138,000	92,290
Restricted shares Vested			64,200	61,800
Time Based Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares Vested			3,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	3.8		3.8
Weighted average expected amortization period			2 years 6 months
Unvested restricted stock awards	414,414		414,414
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Exercised	45,929	27,337	91,217	97,986
Total unrecognized compensation cost	$ 1.2		$ 1.2
Weighted average expected amortization period			2 years 3 months 12 days