Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 State	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Decreased in valuation allowance	$ 14.1
Effective tax rate on pretax (loss)income from continuing operations	18.00%	21.60%	(39.00%)
Uncertain tax benefits accrued	0.4		0.7
Number of individual states subject to income taxes	50
Maximum
Income Taxes [Line Items]
Interest and penalties accrued related to uncertain income tax positions	0.01
Tax years open to examination	2012
Minimum
Income Taxes [Line Items]
Tax years open to examination	2008
State
Income Taxes [Line Items]
Net operating loss carry forwards	$ 99.5