Retirement Benefit Plans - Benefit Cost Assumptions (Details)	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Discount rate	3.20%	3.20%	3.30%
Expected long-term rate of return on plan assets	4.30%	3.80%	3.90%
Rate of compensation increase	2.20%	2.20%	2.20%