Debt (New Zealand Corporate Credit Facility) (Narrative) (Details) $ in Thousands, NZD in Millions		12 Months Ended
	May 21, 2015 NZD	Dec. 31, 2016 NZD item		Dec. 31, 2016 USD ($) item		Dec. 31, 2015 NZD		Dec. 31, 2015 USD ($)		Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Line of credit facility, term		3 years		3 years
Contractual facility | $				$ 266,233				$ 207,075
Westpac Bank Corporate Credit Facility [Member]
Debt Instrument [Line Items]
Contractual facility	NZD 50.0			$ 36,877	[1]			$ 34,210	[2]
Interest rate	1.75%
Maturity date		Mar. 31, 2018	[1]	Mar. 31, 2018	[1]	Mar. 31, 2018	[2]	Mar. 31, 2018	[2]
Number of tranches | item		2		2
New Zealand Corporate Credit Facility, Tranch 1 [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		NZD 53.0								$ 36,900
Line of credit facility, increase in maximum borrowing capacity		3.0		$ 2,100
Contractual facility		50.0				NZD 35.0		$ 23,900
New Zealand Corporate Credit Facility, Tranch 2 [Member]
Debt Instrument [Line Items]
Contractual facility		NZD 18.0		$ 12,500		NZD 15.0		$ 10,300

[1] The contractual facilities and outstanding balances of the FC-denominated borrowings were translated into U.S. dollars based on the applicable exchange rates as of December 31, 2016.

[2] The contractual facilities and outstanding balances of the FC-denominated borrowings were translated into U.S. dollar based on the applicable exchange rates as of December 31, 2015.