Financial Instruments And Investments (Contractual Year For Maturity Of Available-For-Sale Securities ) (Details) $ in Thousands	Jun. 30, 2017 USD ($)
U.S. Government Bonds
Schedule of Available-for-sale Securities [Line Items]
Total	$ 59,050
2017	5,893
2018 through 2021	24,224
2022 through 2026	15,981
2027 and Beyond	12,952
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Total	18,028
2017	796
2018 through 2021	6,215
2022 through 2026	9,743
2027 and Beyond	1,274
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	31,233
2017	0
2018 through 2021	12,309
2022 through 2026	8,949
2027 and Beyond	9,975
Federal Agency Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Total	22,523
2017	0
2018 through 2021	5
2022 through 2026	338
2027 and Beyond	$ 22,180