Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($) securities		Dec. 31, 2015 USD ($) securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	$ 42,068	[1]	$ 73,859	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(626)	[1]	(2,401)	[2]
Marketable Securities Fair Value 12 Months or Longer	22,852	[1]	25,080	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(1,179)	[1]	(1,344)	[2]
Marketable Securities Fair Value Total	64,920	[1]	98,939	[2]
Marketable Securities Unrealized Losses Total	$ (1,805)	[1]	$ (3,745)	[2]
Number of securities | securities	104		133
Debt Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	$ 17,828	[1]	$ 47,821	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(253)	[1]	(1,289)	[2]
Marketable Securities Fair Value 12 Months or Longer	22,852	[1]	25,080	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(1,179)	[1]	(1,344)	[2]
Marketable Securities Fair Value Total	40,680	[1]	72,901	[2]
Marketable Securities Unrealized Losses Total	(1,432)	[1]	(2,633)	[2]
Collateralized Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	1,028	[1]	9,383	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(9)	[1]	(97)	[2]
Marketable Securities Fair Value 12 Months or Longer	0	[1]	1,113	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	0	[1]	(47)	[2]
Marketable Securities Fair Value Total	1,028	[1]	10,496	[2]
Marketable Securities Unrealized Losses Total	(9)	[1]	(144)	[2]
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	8,728	[1]	24,094	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(151)	[1]	(310)	[2]
Marketable Securities Fair Value 12 Months or Longer	12,300	[1]	14,272	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(526)	[1]	(623)	[2]
Marketable Securities Fair Value Total	21,028	[1]	38,366	[2]
Marketable Securities Unrealized Losses Total	(677)	[1]	(933)	[2]
Municipal Bonds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	4,692	[1]	8,286	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(43)	[1]	(160)	[2]
Marketable Securities Fair Value 12 Months or Longer	8,171	[1]	7,388	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(515)	[1]	(446)	[2]
Marketable Securities Fair Value Total	12,863	[1]	15,674	[2]
Marketable Securities Unrealized Losses Total	(558)	[1]	(606)	[2]
Corporate Debt Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	3,380	[1]	6,058	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(50)	[1]	(722)	[2]
Marketable Securities Fair Value 12 Months or Longer	2,381	[1]	2,307	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(138)	[1]	(228)	[2]
Marketable Securities Fair Value Total	5,761	[1]	8,365	[2]
Marketable Securities Unrealized Losses Total	(188)	[1]	(950)	[2]
Equity Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	1,393	[1]	3,584	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(124)	[1]	(344)	[2]
Marketable Securities Fair Value 12 Months or Longer	0	[1]	0	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	0	[1]	0	[2]
Marketable Securities Fair Value Total	1,393	[1]	3,584	[2]
Marketable Securities Unrealized Losses Total	(124)	[1]	(344)	[2]
Institutional Funds-International Equity
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	22,847	[1]	22,454	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(249)	[1]	(768)	[2]
Marketable Securities Fair Value 12 Months or Longer	0	[1]	0	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	0	[1]	0	[2]
Marketable Securities Fair Value Total	22,847	[1]	22,454	[2]
Marketable Securities Unrealized Losses Total	$ (249)	[1]	$ (768)	[2]

[1] Includes 104 securities.

[2] Includes 133 securities.