Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) $ in Thousands	Dec. 31, 2018 USD ($) security
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | security	156
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 35,551	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(882)	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	71,450	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3,627)	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	107,001	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(4,509)	[1]
Federal Agency Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	6,187	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(36)	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	14,567	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(510)	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	20,754	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(546)	[1]
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,005	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	36,615	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,663)	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	40,620	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(1,672)	[1]
Municipal Bonds
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,100	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(74)	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	9,037	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(723)	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	12,137	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(797)	[1]
Corporate Debt Obligations
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	22,259	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(763)	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	11,231	[1]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(731)	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	33,490	[1]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ (1,494)	[1]

[1] Includes approximately 156 securities, aggregated by CUSIP number.