Reconciliation for Assets and Liabilities Measured at Fair Value on Recurring Basis using Significant Unobservable Inputs (Level Three) (Detail) - Common Stock Warrant Liability - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 4.9	$ 8.5	$ 5.6	$ 9.3
Income (Expense) Realized in Earnings	(6.3)	0.2	(5.6)	1.0
Settlements	(0.1)		(0.1)
Ending Balance	$ 11.1	$ 8.3	$ 11.1	$ 8.3