Marketable Securities - Schedule of Marketable Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets
Schedule Of Available For Sale Securities [Line Items]
Market value	$ 1.6	$ 0.9
Cost basis	1.6	0.9
Unrealized gains, net
Noncurrent assets
Schedule Of Available For Sale Securities [Line Items]
Market value	254.1	256.8
Cost basis	254.1	256.7
Unrealized gains, net		0.1
Noncurrent assets \| Other
Schedule Of Available For Sale Securities [Line Items]
Market value	4.1	6.8
Cost basis	4.1	6.7
Unrealized gains, net		0.1
Amalgamated Sugar Company LLC \| Noncurrent assets
Schedule Of Available For Sale Securities [Line Items]
Market value	250.0	250.0
Cost basis	250.0	250.0
Unrealized gains, net

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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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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