Stock Compensation Plans RSU and PSU activity (Details) - $ / shares shares in Millions	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested, Shares, beginning balance	0.6
Granted, Shares	0.3
Vested, Shares	(0.2)
Forfeitures, Shares	(0.1)
Non-vested, Shares, ending balance	0.6	0.6
Non-vested, Weighted Average Grant Date Fair Value, beginning of period	$ 73.33
Granted, Weighted Average Grant Date Fair Value	91.69	$ 67.46	$ 80.44
Vested, Weighted Average Grant Date Fair Value	92.95
Forfeitures, Weighted Average Grant Date Fair Value	78.58
Non-vested, Weighted Average Grant Date Fair Value, end of period	$ 81.12	$ 73.33
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	0.0
Forfeitures, Shares	(0.4)
Non-vested, Shares, ending balance	0.5	0.7
Non-vested, Weighted Average Grant Date Fair Value, beginning of period	$ 73.52
Granted, Weighted Average Grant Date Fair Value	108.99	$ 79.23	$ 58.09
Vested, Weighted Average Grant Date Fair Value	83.45
Forfeitures, Weighted Average Grant Date Fair Value	72.49
Non-vested, Weighted Average Grant Date Fair Value, end of period	$ 84.85	$ 73.52