Gallatin coal combustion residual facilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Other long-term liabilities
Other Long-Term Liabilities
Gallatin coal combustion residual facilities	$ 0	$ 862

Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable after twelve months or beyond the next operating cycle if longer.

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