Borrowings (Westpac Bank Corporate Credit Facility (NZ)) (Narrative) (Details) $ in Thousands, $ in Millions				6 Months Ended			12 Months Ended
	May 07, 2021 NZD ($)	Dec. 20, 2018 NZD ($)	Dec. 19, 2018 NZD ($)	Jun. 30, 2021 USD ($)		Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)		Jul. 27, 2020
Debt Instrument [Line Items]
Contractual facility				$ 274,696			$ 300,449
Repayment of long-term borrowings				75,257		$ 22,311
Westpac Bank Corporate Credit Facility [Member]
Debt Instrument [Line Items]
Contractual facility				$ 11,165	[1]		$ 23,021	[2]
Maturity date				Dec. 31, 2023	[1]		Dec. 31, 2023	[2]
Interest rate		1.10%							1.65%
Repayment of long-term borrowings	$ 16.0
Westpac Bank Corporate Credit Facility [Member] | Bank Bill Swap Bid Rate [Member]
Debt Instrument [Line Items]
Interest rate									2.40%
Westpac Bank Corporate Credit Facility, Tranche 1 [Member]
Debt Instrument [Line Items]
Contractual facility		$ 32.0	$ 35.0
Westpac Bank Corporate Credit Facility, Tranche 1 [Member] | Bank Bill Swap Bid Rate [Member]
Debt Instrument [Line Items]
Interest rate		1.75%
Westpac Bank Corporate Credit Facility, Tranche 2 [Member]
Debt Instrument [Line Items]
Contractual facility		$ 18.0

[1] The contractual facilities and outstanding balances of the foreign currency denominated borrowings were translated into U.S. dollars based on the applicable exchange rates as of June 30, 2021.

[2] The contractual facilities and outstanding balances of the foreign currency denominated borrowings were translated into U.S. dollars based on the applicable exchange rates as of December 31, 2020.