Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) $ in Thousands	Jun. 30, 2019 USD ($) security		Dec. 31, 2018 USD ($) security
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | security	67		156
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 6,598	[1]	$ 35,551	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(337)	[1]	(882)	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	31,874	[1]	71,450	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,187)	[1]	(3,627)	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	38,472	[1]	107,001	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(1,524)	[1]	(4,509)	[2]
Federal Agency Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,021	[1]	6,187	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(20)	[1]	(36)	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	6,654	[1]	14,567	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(96)	[1]	(510)	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	7,675	[1]	20,754	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(116)	[1]	(546)	[2]
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	[1]	4,005	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	[1]	(9)	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	19,763	[1]	36,615	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(867)	[1]	(1,663)	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	19,763	[1]	40,620	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(867)	[1]	(1,672)	[2]
Municipal Obligations
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,800	[1]	3,100	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(315)	[1]	(74)	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	751	[1]	9,037	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(70)	[1]	(723)	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	5,551	[1]	12,137	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	(385)	[1]	(797)	[2]
Corporate Obligations
Financial Instruments and Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	777	[1]	22,259	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)	[1]	(763)	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	4,706	[1]	11,231	[2]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(154)	[1]	(731)	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	5,483	[1]	33,490	[2]
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ (156)	[1]	$ (1,494)	[2]

[1] Includes 67 securities.

[2] Includes 156 securities.