Financial Instruments And Investments (Contractual Year For Maturity Of Available-For-Sale Securities ) (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Federal Agency Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Total	$ 24,465
2018	0
2019 through 2022	15
2023 through 2027	245
2028 and Beyond	24,205
U.S. Government Bonds
Schedule of Available-for-sale Securities [Line Items]
Total	53,533
2018	1,886
2019 through 2022	28,137
2023 through 2027	10,872
2028 and Beyond	12,638
Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Total	13,627
2018	121
2019 through 2022	5,492
2023 through 2027	5,789
2028 and Beyond	2,225
Corporate Obligations
Schedule of Available-for-sale Securities [Line Items]
Total	37,502
2018	0
2019 through 2022	17,303
2023 through 2027	8,471
2028 and Beyond	$ 11,728