Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) - Interest Rate Swap [Member] $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) Caontracts	Dec. 31, 2018 USD ($) Caontracts
2019
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	6	6
Derivative, Notional Amount | $	$ 70,000	$ 70,000
Derivative, Maturity Date	Dec. 31, 2019	Dec. 31, 2019
2020
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	6	6
Derivative, Notional Amount | $	$ 60,000	$ 60,000
Derivative, Maturity Date	Dec. 31, 2020	Dec. 31, 2020
2021
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	2	2
Derivative, Notional Amount | $	$ 25,000	$ 25,000
Derivative, Maturity Date	Dec. 31, 2021	Dec. 31, 2021
2022
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	8	7
Derivative, Notional Amount | $	$ 90,000	$ 80,000
Derivative, Maturity Date	Dec. 31, 2022	Dec. 31, 2022