Equity - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the period				1,555,866
Options outstanding, shares		2,879,370		2,879,370		1,847,669
Shares Issued with debt conversion	348,535
Stock-based compensation expense		$ 4.3	$ 4.2	$ 9.6	$ 8.6
Total unrecognized compensation expense		50.3		50.3
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		2.0	1.3	5.0	2.9
Total unrecognized compensation expense		23.0		23.0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		2.3	$ 2.9	4.6	$ 5.7
Total unrecognized compensation expense		$ 27.3		$ 27.3
Performance based stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the period				184,500
3.75% Convertible Notes
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Principal amount of debt converted	$ 28.5