Other income, net - Schedule of Components of Other Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2011
Securities earnings:
Dividends and interest					$ 21.3	$ 22.0
Securities transactions, net					0.2	(0.6)
Total	7.3	6.6			21.5	21.4
Equity in earnings of investee	(0.1)	(0.1)			(0.1)	(0.3)
Currency transactions, net					(0.6)	0.8
Insurance recoveries	1.2	16.1			2.6	16.6
Litigation settlement gain				14.7	14.7
Reversal of accrued contingent consideration	0.8				0.8
Patent litigation settlement gain			7.5			7.5
Other, net					1.2	0.7
Total	$ 8.2	$ 21.1			$ 40.1	$ 46.7