Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Financial Risk Management - Sensitivity Analysis for Types of Market Risk (Details)

v3.19.3.a.u2
Financial Risk Management - Sensitivity Analysis for Types of Market Risk (Details) - NZD ($)
$ in Thousands
Jan. 31, 2018
Jan. 31, 2017
Jan. 31, 2016
10% Increase [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic $ 200 $ 402 $ 642
10% Decrease [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic (200) (402) (642)
US [Member] | 10% Increase [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic (954) (1,509) (1,196)
US [Member] | 10% Decrease [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic 954 1,509 1,196
AUD [Member] | 10% Increase [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic (5) (805) 86
AUD [Member] | 10% Decrease [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic 5 805 (86)
GBP [Member] | 10% Increase [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic (1) (175) 34
GBP [Member] | 10% Decrease [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic 1 175 (34)
EUR [Member] | 10% Increase [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic (32) (136) 186
EUR [Member] | 10% Decrease [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic 32 136 (186)
HKD [Member] | 10% Increase [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic (1) (14) 1
HKD [Member] | 10% Decrease [Member]      
DisclosureOfFinancialRiskManagementLineItems [Line Items]      
Risk exposure associated with instruments sharing characteristic $ 1 $ 14 $ (1)