Employee Retirement Benefits - The liability and expense reflected in the balance sheet and income statement (Details) - USD ($) $ in Thousands	5 Months Ended		7 Months Ended		12 Months Ended
	Jan. 31, 2016		Aug. 31, 2015		Jan. 31, 2017	Jan. 31, 2016		Jan. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Long-term portion in other liabilities	$ 7,662				$ 8,054	$ 7,662		$ 11,812
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year			$ 12,125		7,991	12,125		8,254
Net periodic benefit cost					399	866		713
Other comprehensive loss (income)					355	(4,697)		3,391
Total recognized in net periodic benefit cost and other comprehensive income					754	(3,831)		4,104
Retiree benefits paid					(329)	(303)		(233)
Benefit obligation at end of year	7,991				8,416	7,991		12,125
Current portion in accrued liabilities	329				362	329		313
Long-term portion in other liabilities	$ 7,662				$ 8,054	$ 7,662		$ 11,812
Assumptions used to calculate benefit obligation:
Discount rate	4.25%				4.00%	4.25%		3.50%
Rate of compensation increase	4.00%				4.00%	4.00%		4.00%
Health care cost trend rate assumed for next year	6.83%	[1]	7.00%	[2]	6.67%			7.20%
Ultimate health care cost trend rate	4.50%	[1]	5.00%	[2]	4.50%			5.00%
Year that the rate reaches the ultimate trend rate	2030	[1]	2025	[2]	2030	2030	[1]	2025
Assumptions used to calculated the net periodic benefit cost:
Discount rate	4.25%	[1]	3.50%	[2]	4.25%			4.50%
Rate of compensation increase					4.00%	4.00%		4.00%
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates
Effect on total of service and interest cost components, one percentage point increase					$ 91
Effect on total of service and interest cost components, one percentage point decrease					(69)
Effect on accumulated postretirement benefit obligation, one percentage point increase					1,486
Effect on accumulated postretirement benefit obligation, one percentage point decrease					(1,159)
2018					362
2019					371
2020					366
2021					379
2022-2027					$ 2,372

[1] Assumptions used for the five months of fiscal 2016 following the August 31, 2015 remeasurement.

[2] Assumptions used for the seven months of fiscal 2016 prior to the plan amendment triggering the August 31, 2015 remeasurement.