Insurance Recoveries On Impairment And Related Losses Due To Earthquake (Allocation Of The Total Insurance Proceeds To The Various Risks and Bases) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 NZD ($)
Insurance Recoveries [Line Items]
Basis for Allocation	$ 55,499
Percentage Allocation	100.00%
Allocation of Insurance Proceeds	$ 36,034
Property Damage [Member]
Insurance Recoveries [Line Items]
Basis for Allocation	$ 44,808
Percentage Allocation	81.00%
Allocation of Insurance Proceeds	$ 29,093
Demolition Costs [Member]
Insurance Recoveries [Line Items]
Basis for Allocation	$ 7,276
Percentage Allocation	13.00%
Allocation of Insurance Proceeds	$ 4,724
Business Interruption [Member]
Insurance Recoveries [Line Items]
Basis for Allocation	$ 3,415
Percentage Allocation	6.00%
Allocation of Insurance Proceeds	$ 2,217