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Consolidated Balance Sheets (Parenthetical) - shares
Mar. 31, 2018
Dec. 31, 2017
Series A Preferred Units [Member]    
Equity:    
Limited partners' capital account, units issued (in shares) 0 12,000,000
Limited Partners' Capital Account, Units Outstanding 0 12,000,000
Common Units [Member]    
Equity:    
Limited partners' capital account, units issued (in shares) 82,492,008 99,667,999
Limited Partners' Capital Account, Units Outstanding 82,492,008 99,667,999
Class C Units - Held by Subsidiary [Member]    
Equity:    
Limited partners' capital account, units issued (in shares) 16,410,780 16,410,780
Limited Partners' Capital Account, Units Outstanding 16,410,780 16,410,780