US Pension Assets, Fair Value Inputs (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	$ 11.2	$ 10.4
Pension Benefits, U.S. Plans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	6.2	8.8
Total	1,167.5	1,177.0
Pension Benefits, U.S. Plans | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	6.2	8.8
Total	435.1	345.1
Pension Benefits, U.S. Plans | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Total	664.4	770.9
Pension Benefits, U.S. Plans | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Total	68.0	61.0
Pension Benefits, U.S. Plans | U.S. Large Cap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	237.4	243.5
Pension Benefits, U.S. Plans | U.S. Large Cap [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | U.S. Large Cap [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	237.4	243.5
Pension Benefits, U.S. Plans | U.S. Large Cap [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | U.S. Mid Cap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	96.4	98.1
Pension Benefits, U.S. Plans | U.S. Mid Cap [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | U.S. Mid Cap [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	96.4	98.1
Pension Benefits, U.S. Plans | U.S. Mid Cap [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | U.S. Small Cap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	176.1	197.6
Pension Benefits, U.S. Plans | U.S. Small Cap [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	131.1	146.9
Pension Benefits, U.S. Plans | U.S. Small Cap [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	45.0	50.7
Pension Benefits, U.S. Plans | U.S. Small Cap [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | International Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	165.4	191.2
Pension Benefits, U.S. Plans | International Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	80.3	0
Pension Benefits, U.S. Plans | International Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	85.1	191.2
Pension Benefits, U.S. Plans | International Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | Emerging Markets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	51.6	64.0
Pension Benefits, U.S. Plans | Emerging Markets [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | Emerging Markets [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	51.6	64.0
Pension Benefits, U.S. Plans | Emerging Markets [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities	0	0
Pension Benefits, U.S. Plans | US Government and Government Agencies and Authorities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	155.2	129.6
Pension Benefits, U.S. Plans | US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	145.7	119.9
Pension Benefits, U.S. Plans | US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	9.5	9.7
Pension Benefits, U.S. Plans | US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	0	0
Pension Benefits, U.S. Plans | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	211.2	183.2
Pension Benefits, U.S. Plans | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	71.8	69.5
Pension Benefits, U.S. Plans | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	139.4	113.7
Pension Benefits, U.S. Plans | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed Income Securities	0	0
Pension Benefits, U.S. Plans | Private Equity Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	23.7	15.0
Pension Benefits, U.S. Plans | Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	0	0
Pension Benefits, U.S. Plans | Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	0	0
Pension Benefits, U.S. Plans | Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	23.7	15.0
Pension Benefits, U.S. Plans | Hedge Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	44.3	46.0
Pension Benefits, U.S. Plans | Hedge Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	0	0
Pension Benefits, U.S. Plans | Hedge Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	0	0
Pension Benefits, U.S. Plans | Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investments	$ 44.3	$ 46.0