Financial Instruments (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2012
Guarantee by the federal government for bonds issued by public agencies			97.00%		97.00%
Discount rate used in internally developed models, minimum			3.60%
Discount rate used in internally developed models, maximum			4.10%
Discount rate used in internally developed models, weighted average			3.90%
Redemption of available-for-sale holdings by issuers of auction rate securities	$ 0	$ 0.1	$ 7.6	$ 0.5
Unrealized loss on available-for-sale auction rate securities	0.1	0.3	(0.4)	(0.6)
Foreign currency forward contracts that closed in a gain position	3.8		3.8		8.1
Foreign currency forward contracts that closed in a loss position	2.3		2.3		0.6
Interest rate swap maturity date			November 2015
Debt instrument, maturity date			November 2015
Interest rate swap liability	0.2		0.2
Hedge ineffectiveness	0		0
Trade finance receivables transferred to financial institutions on a non-recourse basis	43.2	49.0	155.0	208.0
Finance receivables	112.4		112.4
Specific finance receivables fully reserved	0.3		0.3
Unsecured Term Loan Due November 2015 [Member]
Unsecured term loan	200.0		200.0
Foreign Currency Forward Exchange Contract [Member]
Effect of foreign currency forward contracts	4.6	(1.7)	9.2	(7.6)
Net effect of foreign currency forward contracts after including gains and losses on foreign currency exposure	(0.1)	(0.6)	0.6	(2.5)
Auction Rate Securities [Member]
Par value of Auction rate securities held Available-for-sale securities in auction rate securities held			21.7		29.3
Fair value of available-for-sale auction rate securities	18.7		18.7		26.9
Unrealized loss on available-for-sale auction rate securities			3.0
Interest Rate Swap [Member]
Discount rate used in internally developed models, weighted average			1.50%
Derivative notional amount	$ 200.0		$ 200.0
Term Loan [Member]
Discount rate used in internally developed models, weighted average			2.00%