Hedging Instruments - Additional Information (Details)	3 Months Ended	6 Months Ended
	Jul. 31, 2017 USD ($)	Jul. 31, 2018 USD ($) oz	Jul. 31, 2017 USD ($)
Derivative [Line Items]
Pre-tax losses on derivatives not designated as hedging instruments	$ 2,900,000		$ 2,500,000
Expected approximate amount of net pre-tax derivative losses included in accumulated other comprehensive income that will be reclassified into earnings within the next 12 months		$ 3,600,000
2012 4.40% Series B Notes, due July 2042 [Member]
Derivative [Line Items]
Debt, par amount		250,000,000
Interest Rate Swap [Member] | 2012 Debt Issuance [Member]
Derivative [Line Items]
Unrealized loss on interest rate swaps		17,900,000
Interest Rate Swap [Member] | 2014 Debt Issuance [Member]
Derivative [Line Items]
Unrealized loss on interest rate swaps		$ 3,600,000
Foreign exchange forward contracts [Member] | Maximum [Member]
Derivative [Line Items]
Derivative, term of contract (in months)		12 months
Precious metal forward contracts [Member] | Maximum [Member]
Derivative [Line Items]
Derivative, term of contract (in months)		18 months
Platinum [Member]
Derivative [Line Items]
Notional amount of precious metal hedge (in ounces) | oz		42,200
Silver [Member]
Derivative [Line Items]
Notional amount of precious metal hedge (in ounces) | oz		810,000
Gold [Member]
Derivative [Line Items]
Notional amount of precious metal hedge (in ounces) | oz		85,700