Summary Of Significant Accounting Policies (Summary Of Currency Exchange Rates) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Australian Dollar [Member] | Spot Rate [Member]
Currency Exchange Rates [Line Items]
Foreign currency exchange rate	0.7815	0.7230	0.7286
Australian Dollar [Member] | Average Rate [Member]
Currency Exchange Rates [Line Items]
Foreign currency exchange rate	0.7670	0.7440	0.7524
New Zealand Dollar [Member] | Spot Rate [Member]
Currency Exchange Rates [Line Items]
Foreign currency exchange rate	0.7100	0.6958	0.6842
New Zealand Dollar [Member] | Average Rate [Member]
Currency Exchange Rates [Line Items]
Foreign currency exchange rate	0.7111	0.6973	0.7004