Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) - Interest Rate Swap Agreements [Member] $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($) Caontracts	Dec. 31, 2015 USD ($) Caontracts
2016 [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	6	6
Derivative, Notional Amount | $	$ 115,000	$ 115,000
Derivative, Maturity Date	Dec. 31, 2016	Dec. 31, 2016
2017 [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	4	3
Derivative, Notional Amount | $	$ 55,000	$ 45,000
Derivative, Maturity Date	Dec. 31, 2017	Dec. 31, 2017
2018 [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	13	11
Derivative, Notional Amount | $	$ 265,000	$ 245,000
Derivative, Maturity Date	Dec. 31, 2018	Dec. 31, 2018
2019 [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	3	2
Derivative, Notional Amount | $	$ 40,000	$ 30,000
Derivative, Maturity Date	Dec. 31, 2019	Dec. 31, 2019
2022 [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	4	1
Derivative, Notional Amount | $	$ 50,000	$ 20,000
Derivative, Maturity Date	Dec. 31, 2022	Dec. 31, 2022