XML 57 R47.htm IDEA: XBRL DOCUMENT v3.8.0.1
Financial Instruments And Investments (Marketable Securities Fair Value and Unrecognized Gross Unrealized Gains) (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Gross Unrealized Gain $ 47,047 $ 38,667
Marketable Securities Fair Value, Total 192,690 144,628
Debt Securities    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 45,749 34,498
Available-for-sale Securities, Gross Unrealized Gain 1,705 1,256
Federal Agency Mortgage Backed Securities    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 8,662 7,430
Available-for-sale Securities, Gross Unrealized Gain 267 319
U.S. Government Bonds    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 13,844 12,237
Available-for-sale Securities, Gross Unrealized Gain 309 138
Municipal Obligations    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 4,206 2,481
Available-for-sale Securities, Gross Unrealized Gain 139 144
Corporate Obligations    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 19,037 12,350
Available-for-sale Securities, Gross Unrealized Gain 990 655
Common Stock    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 52,809 61,884
Available-for-sale Securities, Gross Unrealized Gain 31,343 34,066
Equity Mutual Funds    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 59,971 42,244
Available-for-sale Securities, Gross Unrealized Gain 9,201 3,345
Institutional Funds-International Equity    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Unrealized Gain Position, Fair Value 27,734 0
Available-for-sale Securities, Gross Unrealized Gain 4,798 0
Cash    
Financial Instruments and Investments [Line Items]    
Available-for-sale Securities, Gross Unrealized Gain 0 0
Cash | Held in trust Decommissioning Fund Investment    
Financial Instruments and Investments [Line Items]    
Cash $ 6,427 $ 6,002