Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) Caontracts	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) Caontracts
Derivatives, Fair Value [Line Items]
Payments for (Proceeds from) Derivative Instrument, Financing Activities	$ (9,326)	$ 0
Secured Debt	$ 1,511,700		$ 1,511,700
2016 [Member] | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	6		5
Derivative, Notional Amount	$ 115,000		$ 95,000
Derivative, Maturity Date	Dec. 31, 2016		Dec. 31, 2016
2015 [Member] | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Swaps Settled | Caontracts	5
Number of contracts | Caontracts			5
Derivative, Notional Amount			$ 75,000
Settled Derivative, Notional Amount	$ 75,000
Derivative, Maturity Date			Dec. 31, 2015
2017 [Member] | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	3		3
Derivative, Notional Amount	$ 45,000		$ 45,000
Derivative, Maturity Date	Dec. 31, 2017		Dec. 31, 2017
2018 [Member] | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	11		9
Derivative, Notional Amount	$ 245,000		$ 205,000
Derivative, Maturity Date	Dec. 31, 2018		Dec. 31, 2018
2019 [Member] | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	1
Derivative, Notional Amount	$ 20,000
Derivative, Maturity Date	Dec. 31, 2019