Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) securities		Dec. 31, 2015 USD ($) securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	$ 41,646	[1]	$ 73,859	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(2,206)	[1]	(2,401)	[2]
Marketable Securities Fair Value 12 Months or Longer	26,405	[1]	25,080	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(1,313)	[1]	(1,344)	[2]
Marketable Securities Fair Value Total	68,051	[1]	98,939	[2]
Marketable Securities Unrealized Losses Total	$ (3,519)	[1]	$ (3,745)	[2]
Number of securities | securities	105		133
Debt Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	$ 16,349	[1]	$ 47,821	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(265)	[1]	(1,289)	[2]
Marketable Securities Fair Value 12 Months or Longer	26,405	[1]	25,080	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(1,313)	[1]	(1,344)	[2]
Marketable Securities Fair Value Total	42,754	[1]	72,901	[2]
Marketable Securities Unrealized Losses Total	(1,578)	[1]	(2,633)	[2]
Collateralized Mortgage Backed Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	996	[1]	9,383	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(2)	[1]	(97)	[2]
Marketable Securities Fair Value 12 Months or Longer	1,109	[1]	1,113	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(23)	[1]	(47)	[2]
Marketable Securities Fair Value Total	2,105	[1]	10,496	[2]
Marketable Securities Unrealized Losses Total	(25)	[1]	(144)	[2]
U.S. Government Bonds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	8,656	[1]	24,094	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(51)	[1]	(310)	[2]
Marketable Securities Fair Value 12 Months or Longer	13,666	[1]	14,272	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(501)	[1]	(623)	[2]
Marketable Securities Fair Value Total	22,322	[1]	38,366	[2]
Marketable Securities Unrealized Losses Total	(552)	[1]	(933)	[2]
Municipal Bonds
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	3,569	[1]	8,286	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(42)	[1]	(160)	[2]
Marketable Securities Fair Value 12 Months or Longer	8,681	[1]	7,388	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(513)	[1]	(446)	[2]
Marketable Securities Fair Value Total	12,250	[1]	15,674	[2]
Marketable Securities Unrealized Losses Total	(555)	[1]	(606)	[2]
Corporate Debt Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	3,128	[1]	6,058	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(170)	[1]	(722)	[2]
Marketable Securities Fair Value 12 Months or Longer	2,949	[1]	2,307	[2]
Marketable Securities Unrealized Losses 12 Months or Longer	(276)	[1]	(228)	[2]
Marketable Securities Fair Value Total	6,077	[1]	8,365	[2]
Marketable Securities Unrealized Losses Total	(446)	[1]	(950)	[2]
Equity Securities
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	3,441	[1]	3,584	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(620)	[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	3,441	[1]	3,584	[2]
Marketable Securities Unrealized Losses Total	(620)	[1]	(344)	[2]
Institutional Funds-International Equity
Financial Instruments and Investments [Line Items]
Marketable Securities Fair Value Less than 12 Months	21,856	[1]	22,454	[2]
Marketable Securities Unrealized Losses Less Than 12 Months	(1,321)	[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	21,856	[1]	22,454	[2]
Marketable Securities Unrealized Losses Total	$ (1,321)	[1]	$ (768)	[2]

[1] Includes 105 securities.

[2] Includes 133 securities.