Employee Benefit Plans - Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Earnings (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial loss	$ 15,993	$ 7,042	$ 2,787
Recognized prior service (cost) credit	356	406	419
Net unrealized loss on benefit plans	(18,171)	(118,366)	(11,365)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	18,058	14,105	12,741
Interest cost	26,796	25,321	23,860
Expected return on plan assets	(20,416)	(18,716)	(17,568)
Amortization of prior service cost	1,015	1,065	1,078
Amortization of net loss	15,964	7,026	2,786
Net periodic benefit cost	41,417	28,801	22,897
Net actuarial loss	34,080	116,703	10,583
Recognized actuarial loss	(15,964)	(7,026)	(2,786)
Recognized prior service (cost) credit	(1,015)	(1,065)	(1,078)
Net unrealized loss on benefit plans	17,101	108,612	6,719
Total recognized in net periodic benefit cost and other comprehensive earnings	58,518	137,413	29,616
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,382	2,198	1,711
Interest cost	2,839	3,101	2,943
Expected return on plan assets
Amortization of prior service cost	(659)	(659)	(659)
Amortization of net loss	29	16	1
Net periodic benefit cost	4,591	4,656	3,996
Net actuarial loss	440	9,111	3,988
Recognized actuarial loss	(29)	(16)	(1)
Recognized prior service (cost) credit	659	659	659
Net unrealized loss on benefit plans	1,070	9,754	4,646
Total recognized in net periodic benefit cost and other comprehensive earnings	$ 5,661	$ 14,410	$ 8,642