Income Taxes - Schedule of Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Income Tax Assets And Liabilities [Line Items]
Net operating losses	$ 12.3	$ 9.7
Accrual for post-retirement benefits other than pensions	4.5	4.1
Environmental reserves	4.5	4.9
Retained liabilities of previously owned businesses	8.5	4.7
Accruals and reserves	5.4	7.8
Pensions	13.6	13.3
Minimum pension liability	38.3	38.2
Inventories	6.0	4.3
Interest	6.3	4.7
Compensation and benefits	9.3	8.9
Gross deferred income tax assets	108.7	100.6
Valuation allowance	(17.7)	(12.1)
Total deferred income tax assets	91.0	88.5
Depreciation and amortization	(36.1)	(33.4)
GST deconsolidation gain	(21.4)	(21.0)
Total deferred income tax liabilities	(57.5)	(54.4)
Net deferred tax assets	$ 33.5	$ 34.1