Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Long-term debt | $ 630.9 | $ 630.9 |
| Long-term debt-affiliated, Estimated Fair Value | $ 683.2 | $ 630.9 |