Borrowings (Westpac Bank Corporate Credit Facility (NZ)) (Narrative) (Details) $ in Thousands, $ in Millions						12 Months Ended
	Aug. 30, 2021 NZD ($)	May 07, 2021 NZD ($)	Jun. 29, 2020	Dec. 20, 2018 NZD ($)	Dec. 19, 2018 NZD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Contractual facility						$ 248,948	$ 300,449
Repayment of long-term borrowings						88,417	29,896	$ 52,394
Westpac Bank Corporate Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, increase in maximum borrowing capacity	$ 13.8	$ 16.0
Contractual facility						$ 9,465	$ 23,021
Maturity date						Dec. 31, 2023	Dec. 31, 2023
Interest rate			1.65%
Repayment of long-term borrowings	$ 2.2	$ 16.0
Westpac Bank Corporate Credit Facility [Member] | Bank Bill Swap Bid Rate [Member]
Debt Instrument [Line Items]
Increase in spread on variable interest rate			2.40%
Westpac Bank Corporate Credit Facility, Tranche 1 [Member]
Debt Instrument [Line Items]
Line of credit facility, increase in maximum borrowing capacity				$ 32.0	$ 35.0
Interest rate				1.10%
Westpac Bank Corporate Credit Facility, Tranche 1 [Member] | Bank Bill Swap Bid Rate [Member]
Debt Instrument [Line Items]
Increase in spread on variable interest rate				1.75%
Westpac Bank Corporate Credit Facility, Tranche 2 [Member]
Debt Instrument [Line Items]
Line of credit facility, increase in maximum borrowing capacity				$ 18.0