Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, non-trade	$ 8,183	$ 32,387
Accumulated depreciation	$ 1,634,394	$ 1,562,172
Convertible Preferred Units
Convertible Preferred Units, units issued	0	0
Convertible Preferred Units, units outstanding	0	0
Common Units
Limited partners, units issued	410,300,000	410,000,000
Limited partners, units outstanding	410,300,000	410,000,000
Preferred Units
Limited partners, units issued	15,800,000	11,000,000
Limited partners, units outstanding	15,800,000	11,000,000

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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The number of limited partner units issued.

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