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Quarterly report pursuant to Section 13 or 15(d)

ASSET RETIREMENT OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details)

v3.20.1
ASSET RETIREMENT OBLIGATIONS (Asset Retirement Obligation Disclosure) (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Asset Retirement Obligation [Roll Forward] Ìý Ìý
Asset retirement obligation at beginning of period $ 165.3 [1] $ 172.4
Increase from AK Steel acquisition 13.9 0.0
Accretion expense 2.6 10.1
Remediation payments (0.4) (0.8)
Revision in estimated cash flows 0.0 (16.4)
Asset retirement obligation at end of period [1] $ 181.4 $ 165.3
[1]
1 Includes $32.5 million and $22.0 million related to our active operations as of March 31, 2020 and December 31, 2019, respectively.