Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			1 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Oct. 31, 2011 Income Tax Refund
Income Taxes [Line Items]
Continuing operations, effective tax rate	36.60%	37.80%	37.50%	38.20%
Unrecognized tax benefits, net of federal tax benefit, if recognized, would impact effective tax rate	$ 1.9		$ 1.9		$ 2.2
Tax benefit (expense), recognized	0.4	0.9
Federal income tax refund received						26.2
Accrued liability for the payment of interest and penalties	0.7		0.7		0.8
Remaining unrecognized tax positions	$ 0.5		$ 0.5