Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense or benefit	$ 0.1	$ 0.1	$ 0
Gross deferred tax assets	39.4	39.4
Valuation allowance for net deferred tax assets	31.4	31.4
Net deferred tax assets	8.0	8.0
Deferred tax liabilities	8.0	8.0
Short term deferred tax liabilities	0.8	0.8
Current net deferred tax liabilities	7.2	7.2	7.3	7.1
Net long term deferred tax assets	$ 7.2	$ 7.2	$ 7.3	$ 7.1