Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Valuation Allowance [Line Items]
Federal net operating loss carryforward	$ 203.8
State net operating loss carryforwards	47.8
Valuation allowance before taxes	41.0	30.0
Deferred tax assets classified as a current income tax receivable	31.2
Proceeds from income tax returns due to operating loss carryforwards	32
Liabilities for unrecognized tax benefits	0	0
Interest and penalty charges	$ 0	$ 0	$ 0
Federal
Valuation Allowance [Line Items]
Operating loss carryforward Expiration Date	2031
State and Local Jurisdiction | Minimum
Valuation Allowance [Line Items]
Operating loss carryforward Expiration Date	2024
State and Local Jurisdiction | Maximum
Valuation Allowance [Line Items]
Operating loss carryforward Expiration Date	2032