Financial Instruments And Investments (Company's Decommissioning Trust Funds And Investments In Debt Securities) (Details) - USD ($)
$ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Dec. 31, 2014 |
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Cash and Cash Equivalents, at Carrying Value |
$ 10,044
|
$ 8,149
|
$ 12,573
|
$ 40,504
|
| Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
254,626
|
239,035
|
|
|
| Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
190,561
|
176,130
|
|
|
| Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
64,065
|
62,905
|
|
|
| Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Debt Securities |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Trading Securities |
1,398
|
1,543
|
|
|
| Debt Securities | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Trading Securities |
0
|
0
|
|
|
| Debt Securities | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Trading Securities |
0
|
0
|
|
|
| Debt Securities | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Trading Securities |
1,398
|
1,543
|
|
|
| Debt Securities | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
120,804
|
113,304
|
|
|
| Debt Securities | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
56,739
|
50,399
|
|
|
| Debt Securities | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
64,065
|
62,905
|
|
|
| Debt Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| U.S. Government Bonds | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
56,739
|
50,399
|
|
|
| U.S. Government Bonds | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
56,739
|
50,399
|
|
|
| U.S. Government Bonds | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| U.S. Government Bonds | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Collateralized Mortgage Backed Securities | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
17,800
|
20,085
|
|
|
| Collateralized Mortgage Backed Securities | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Collateralized Mortgage Backed Securities | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
17,800
|
20,085
|
|
|
| Collateralized Mortgage Backed Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Municipal Bonds | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
22,136
|
24,345
|
|
|
| Municipal Bonds | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Municipal Bonds | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
22,136
|
24,345
|
|
|
| Municipal Bonds | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Corporate Debt Securities | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
24,129
|
18,475
|
|
|
| Corporate Debt Securities | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Corporate Debt Securities | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
24,129
|
18,475
|
|
|
| Corporate Debt Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Equity Securities | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
67,448
|
76,220
|
|
|
| Equity Securities | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
67,448
|
76,220
|
|
|
| Equity Securities | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Equity Securities | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Equity Funds | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
35,552
|
18,853
|
|
|
| Equity Funds | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
35,552
|
18,853
|
|
|
| Equity Funds | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Equity Funds | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Institutional Funds-International Equity | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
22,847
|
22,454
|
|
|
| Institutional Funds-International Equity | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
22,847
|
22,454
|
|
|
| Institutional Funds-International Equity | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Institutional Funds-International Equity | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Available-for-sale Securities |
0
|
0
|
|
|
| Cash and Cash Equivalents |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Cash and Cash Equivalents, at Carrying Value |
7,975
|
8,204
|
|
|
| Cash and Cash Equivalents | Decommisioning Fund Investments |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Cash and Cash Equivalents, at Carrying Value |
7,975
|
8,204
|
|
|
| Cash and Cash Equivalents | Decommisioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Cash and Cash Equivalents, at Carrying Value |
7,975
|
8,204
|
|
|
| Cash and Cash Equivalents | Decommisioning Fund Investments | Significant Other Observable Inputs (Level 2) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Cash and Cash Equivalents, at Carrying Value |
0
|
0
|
|
|
| Cash and Cash Equivalents | Decommisioning Fund Investments | Significant Unobservable Inputs (Level 3) |
|
|
|
|
| Financial Instruments and Investments [Line Items] |
|
|
|
|
| Cash and Cash Equivalents, at Carrying Value |
$ 0
|
$ 0
|
|
|