Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Deferred Tax Liability Not Recognized [Line Items]
Total unrecognized tax benefits	$ 1.7	$ 1.7
Accrued interest (net of tax benefit) related to uncertain tax positions	0	0
Deferred tax assets, valuation allowance adjustment	0.7
Deferred tax assets, valuation allowance	96.1	95.5
Deferred tax assets, provision for valuation allowance	3.7	3.8
Deferred tax assets, decrease in valuation allowance	0.1
Internal Revenue Service (IRS)
Deferred Tax Liability Not Recognized [Line Items]
Net operating loss carryforward	93.6	92.0
State and Local Jurisdiction
Deferred Tax Liability Not Recognized [Line Items]
Net operating loss carryforward	$ 614.2	$ 612.6