Hedging Instruments - Additional Information (Detail) (USD $)	6 Months Ended					6 Months Ended
	Jul. 31, 2014	Jul. 31, 2014 Foreign Exchange Contract [Member] Not Designated as Hedging Instrument [Member]	Jul. 31, 2014 Foreign Exchange Contract [Member] Cash Flow Hedging [Member]	Jul. 31, 2014 Platinum [Member] Precious Metal Forward Contracts [Member] Cash Flow Hedging [Member] oz	Jul. 31, 2014 Silver [Member] Precious Metal Forward Contracts [Member] Cash Flow Hedging [Member] oz	Jul. 31, 2014 Minimum [Member] Foreign Exchange Contract [Member]	Jul. 31, 2014 Maximum [Member] Foreign Exchange Contract [Member]	Jul. 31, 2014 Maximum [Member] Precious Metal Forward Contracts [Member]	Jan. 31, 2013 2012 4.40% Series B Notes, due July 2042 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Debt Instrument, Face Amount									$ 250,000,000
Derivative, Notional Amount		57,027,000	163,106,000
Derivative, Term of Contract						1 month	12 months	12 months
Notional amount of precious metal hedge				14,900	454,100
Expected approximately amount of net pre-tax derivative gains included in accumulated other comprehensive income that will be reclassified into earnings within the next 12 months	$ 3,800,000