Debt Long Term Debt Table (Details) (USD $)	Jan. 31, 2015		Jan. 31, 2014
Debt Instrument [Line Items]
Long-term Debt	$ 882,535,000		$ 751,154,000
2008 9.05% Series A, due December 2015 [Member]
Debt Instrument [Line Items]
Long-term Debt	0	[1],[2]	103,804,000	[1],[2]
2009 10.00% Series A, due April 2018 [Member]
Debt Instrument [Line Items]
Long-term Debt	0	[1]	50,000,000	[1]
2009 10.00% Series A, due February 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	0	[1]	125,000,000	[1]
2009 10.00% Series B, due February 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt	0	[1]	125,000,000	[1]
2010 1.72% Notes, due September 2016 [Member]
Debt Instrument [Line Items]
Long-term Debt	84,470,000	[3],[4]	97,350,000	[3],[4]
2012 4.40% Series B Notes, due July 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt	250,000,000	[5]	250,000,000	[5]
2014 3.80% Senior Notes, due October 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt	249,277,000	[3],[6]	0	[3],[6]
2014 4.90% Senior Notes, due October 2044 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 298,788,000	[3],[6]	$ 0	[3],[6]

[1] aThese Notes were redeemed with the net proceeds from the offering of the 2024 Notes and the 2044 Notes

[2] bThese Notes were issued, at par, $100,000,000. In 2009, the Company entered into an interest rate swap to effectively convert this fixed rate obligation to a floating rate obligation. The Company terminated the interest rate swap in 2011 and recognized the remaining gain on the swap upon redemption of these Notes.

[3] c These agreements require lump sum repayments upon maturity.

[4] d These Notes were issued, at par, ¥10,000,000,000

[5] e The agreements governing these Notes require repayments of $50,000,000 in aggregate every five years beginning in 2022.

[6] f These Notes were issued at a discount which will be amortized until the debt maturity.