Financial Instruments And Investments (Marketable Securities Fair Value and Unrecognized Gross Unrealized Gains) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	$ 27,181
Available-for-sale Securities, Gross Unrealized Gain	667
Federal Agency Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	9,959
Available-for-sale Securities, Gross Unrealized Gain	176
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	6,987
Available-for-sale Securities, Gross Unrealized Gain	149
Municipal Bonds
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	1,952
Available-for-sale Securities, Gross Unrealized Gain	120
Corporate Debt Obligations
Financial Instruments and Investments [Line Items]
Available-for-sale Securities, Unrealized Gain Position, Fair Value	8,283
Available-for-sale Securities, Gross Unrealized Gain	$ 222