Marketable securities - Schedule of Marketable Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Current Assets [Member]
Market value	$ 0.8	$ 22.5
Cost basis	0.8	22.7
Unrealized gains/(losses), net		(0.2)
Current Assets [Member] \| Mutual Funds [Member]
Market value		20.9
Cost basis		21.1
Unrealized gains/(losses), net		(0.2)
Current Assets [Member] \| Other [Member]
Market value		1.6
Cost basis		1.6
Noncurrent Assets [Member]
Market value	338.9	354.1
Cost basis	341.1	342.5
Unrealized gains/(losses), net	(2.2)	11.6
Noncurrent Assets [Member] \| Other [Member]
Market value	5.2	6.4
Cost basis	5.1	6.5
Unrealized gains/(losses), net	0.1	(0.1)
Noncurrent Assets [Member] \| Amalgamated Sugar Company LLc [Member]
Market value	250.0	250.0
Cost basis	250.0	250.0
Noncurrent Assets [Member] \| TIMET Common Stock [Member]
Market value	83.7	97.7
Cost basis	86.0	86.0
Unrealized gains/(losses), net	$ (2.3)	$ 11.7

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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