Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Accounts receivable, allowance for credit loss, current	$ 0.5	$ 0.5
Accumulated depreciation	3,863.0	3,418.6
Accumulated amortization	$ 668.8	$ 545.9
Members’ equity:
Common units issued (in shares)	489,381,149	487,791,612
Common units outstanding (in shares)	489,381,149	487,791,612

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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