Share-Based Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 plan	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans in effect	1
Share based compensation, number of options terminated (in shares)	314,153
Performance-based liability awards, measurement period	3 years
Percentage of award to be paid in cash	50.00%
Compensation expense related to cash awards	$ 0.3	$ 0.6
Share-based compensation expenses	0.5	0.5
Share based compensation, restricted stock options description	Per the plan 50% vested on the date of the grant and the balance vest on the first anniversary of the date of the grant.
Total unrecognized compensation expense	$ 6.8
Total unrecognized compensation expense, weighted average period of recognition	4 years 10 months 24 days
Long-Term Incentive Plan ("LTIP")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for grant	2,000,000
Share based compensation, number of options available for issuance (in shares)	1,622,452
Service-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service based restricted stock, shares granted during period	93,565
Service based restricted stock, vesting period	5 years