Stock Compensation Plans RSU and PSU activity (Details) - $ / shares shares in Millions	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested, Shares, beginning balance	0.5
Granted, Shares	0.4
Vested, Shares	(0.2)
Forfeitures, Shares	(0.1)
Non-vested, Shares, ending balance	0.6	0.5
Non-vested, Weighted Average Grant Date Fair Value, beginning of period	$ 79.02
Granted, Weighted Average Grant Date Fair Value	67.46	$ 80.44	$ 90.68
Vested, Weighted Average Grant Date Fair Value	71.29
Forfeitures, Weighted Average Grant Date Fair Value	79.51
Non-vested, Weighted Average Grant Date Fair Value, end of period	$ 73.33	$ 79.02
Performance Based Restricted Stock units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested, Shares, beginning balance	0.7
Granted, Shares	0.2
Vested, Shares	(0.1)
Forfeitures, Shares	(0.1)
Non-vested, Shares, ending balance	0.7	0.7
Non-vested, Weighted Average Grant Date Fair Value, beginning of period	$ 70.56
Granted, Weighted Average Grant Date Fair Value	79.23	$ 58.09	$ 82.88
Vested, Weighted Average Grant Date Fair Value	67.15
Forfeitures, Weighted Average Grant Date Fair Value	69.85
Non-vested, Weighted Average Grant Date Fair Value, end of period	$ 73.52	$ 70.56