Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax expense or benefit	$ 0	$ 0.1	$ 0	$ 0.1
Gross deferred tax assets	38.1		38.1
Valuation allowance for net deferred tax assets	29.7		29.7
Net deferred tax assets	8.4		8.4
Deferred tax liabilities	8.4		8.4
Short term deferred tax liabilities	0.9		0.9
Current net deferred tax liabilities	7.5	7.2	7.5	7.2	7.9
Long term deferred tax assets	$ 7.5	$ 7.2	$ 7.5	$ 7.2	$ 7.9