US Changes in Assets measured at fair value using signifcant unobservable inputs (Detail) (Pension Benefits, U.S. Plans, Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Beginning of Year	$ 68.0	$ 61.0
Actual Return on Plan Assets Held at Year End	4.3	1.4
Actual Return on Plan Assets Sold During the Year	1.0	(0.1)
Purchases	17.8	13.4
Sales	(6.3)	(7.7)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
End of Year	84.8	68.0
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning of Year	23.7	15.0
Actual Return on Plan Assets Held at Year End	0.5	3.0
Actual Return on Plan Assets Sold During the Year	1.0	0
Purchases	6.0	6.5
Sales	(2.5)	(0.8)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
End of Year	28.7	23.7
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning of Year	44.3	46.0
Actual Return on Plan Assets Held at Year End	3.8	(1.6)
Actual Return on Plan Assets Sold During the Year	0	(0.1)
Purchases	11.8	6.9
Sales	(3.8)	(6.9)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
End of Year	$ 56.1	$ 44.3