LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS (Environmental Matters) (Details) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($) state tank	Dec. 31, 2018 USD ($)
Underground fuel storage tanks
Environmental Matters
Number of underground tanks where the company's subsidiaries store fuel for use in tractors and trucks \| tank	61
Number of states in which underground tanks are located \| state	18
Environmental cleanup costs \| Accrued expenses
Environmental Matters
Reserve for environmental contingencies \| $	$ 0.6	$ 0.6

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

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