Financial Instruments And Investments (Contractual Year For Maturity Of Available-For-Sale Securities ) (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Federal Agency Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Total	$ 21,717
2017	0
2018 through 2021	5
2022 through 2026	316
2027 and Beyond	21,396
U.S. Government Bonds
Schedule of Available-for-sale Securities [Line Items]
Total	58,744
2017	3,343
2018 through 2021	24,151
2022 through 2026	15,959
2027 and Beyond	15,291
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Total	17,848
2017	487
2018 through 2021	6,160
2022 through 2026	9,938
2027 and Beyond	1,263
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	31,883
2017	0
2018 through 2021	13,172
2022 through 2026	8,997
2027 and Beyond	$ 9,714