Share-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock option exercised	400,000	300,000
Cash received from stock option exercises	$ 3.0	$ 1.0
Common stock issued pursuant to the vesting of restricted stock units (RSUs)	93,000
Stock options granted	800,000	700,000
Stock vesting period	4 years
Stock option contractual life	10 years
Share-based compensation expense	2.4	1.7
Due to Changes in the Plan | Scenario, Previously Reported
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock option contractual life	7 years
Restricted Stock Units (RSUs)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized compensation cost	9.5
Unrecognized compensation cost, weighted average period of recognition	3 years 7 months 6 days
Stock vesting period	4 years	4 years
Share-based compensation expense	0.5	0.2
Restricted stock units granted	400,000	400,000
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized compensation cost	17.1
Unrecognized compensation cost, weighted average period of recognition	3 years
Stock vesting period	4 years
Share-based compensation expense	1.9	1.5
Performance-based RSUs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized compensation cost	9.3
RSU with performance-based vesting requirements outstanding	500,000
Stock vesting period	5 years
Share-based compensation expense	$ 0
Restricted stock units granted	500,000