Employee Benefit Plans - Schedule of Net Periodic Pension and Other Postretirement Benefit Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 4,226	$ 4,783	$ 12,707	$ 14,360
Interest Cost	7,064	6,752	21,195	20,256
Expected Return on Plan Assets	(5,909)	(5,560)	(17,727)	(16,680)
Amortization of Prior Service Cost (Credit)	69	243	206	729
Amortization of net loss	3,281	4,753	9,845	14,258
Net expense	8,731	10,971	26,226	32,923
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	581	698	1,745	2,094
Interest Cost	662	691	1,985	2,072
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Cost (Credit)	(168)	(165)	(505)	(495)
Amortization of net loss	5	53	15	159
Net expense	$ 1,080	$ 1,277	$ 3,240	$ 3,830