Debt Long Term Debt Table (Details) - USD ($) $ in Millions		Jan. 31, 2017	Jan. 31, 2016
Debt Instrument [Line Items]
Long-term debt, including current maturities		$ 888.0	$ 884.2
Current portion of long-term debt		0.0	84.2
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		9.6	10.0
Long-term debt		878.4	790.0
2010 1.72% Notes, due September 2016 [Member]
Debt Instrument [Line Items]
Long-term debt, including current maturities	[1],[2]	0.0	84.2
2012 4.40% Series B Notes, due July 2042 [Member]
Debt Instrument [Line Items]
Long-term debt, including current maturities	[3]	250.0	250.0
2014 3.80% Senior Notes, due October 2024 [Member]
Debt Instrument [Line Items]
Long-term debt, including current maturities	[4],[5]	250.0	250.0
2014 4.90% Senior Notes, due October 2044 [Member]
Debt Instrument [Line Items]
Long-term debt, including current maturities	[4],[5]	300.0	300.0
2016 0.78% Senior Notes, due August 2026 [Member]
Debt Instrument [Line Items]
Long-term debt, including current maturities	[1],[5]	$ 88.0	$ 0.0

[1] These Senior Notes were issued, at par, ¥10.0 billion.

[2] These Senior Notes were repaid upon the maturity thereof during the year ended January 31, 2017 using the proceeds from the issuance of the 0.78% Senior Notes due August 2026.

[3] The agreements governing these Senior Notes require repayments of $50.0 million in aggregate every five years beginning in July 2022.

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

[5] These agreements require lump sum repayments upon maturity.