Components of Gas Inventory (Detail) - USD ($) $ in Millions |
Jun. 30, 2016 |
Dec. 31, 2015 |
Jun. 30, 2015 |
|---|---|---|---|
| Public Utilities, Inventory [Line Items] | |||
| Weighted average cost inventory amount | $ 0.4 | $ 0.8 | $ 0.5 |
| Liquefied Natural Gas & Other | |||
| Public Utilities, Inventory [Line Items] | |||
| Weighted average cost inventory amount | 0.1 | 0.2 | 0.1 |
| Natural Gas | |||
| Public Utilities, Inventory [Line Items] | |||
| Weighted average cost inventory amount | 0.1 | 0.3 | 0.2 |
| Propane | |||
| Public Utilities, Inventory [Line Items] | |||
| Weighted average cost inventory amount | $ 0.2 | $ 0.3 | $ 0.2 |