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Commitments and Contingencies, Liquidity Option Agreement (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Line Items]        
Federal corporate tax rate (in hundredths)   35.00%    
Liquidity Option Agreement [Abstract]        
Change in fair value of Liquidity Option Agreement   $ 64.3 $ 24.5 $ 25.4
Percentage of capital stock we agreed to purchase under liquidity option agreement   100.00%    
Liquidity Option exercise period   90 days    
Percentage of fair market value of Enterprise units to be paid as consideration   100.00%    
Trigger Event exercise period   135 days    
Number of units held by limited partner (in units)   54,807,352    
Liquidity Option Agreement [Member]        
Liquidity Option Agreement [Abstract]        
Increase in fair value of liquidity option agreement due to Tax Cuts and Jobs Act   $ 21.2    
Increase in fair value of liquidity option agreement assuming retention of all units   40.2    
Plan [Member]        
Income Tax Disclosure [Line Items]        
Federal corporate tax rate (in hundredths) 21.00%      
Level 3 [Member]        
Liquidity Option Agreement [Abstract]        
Liquidity option agreement   $ 333.9 $ 269.6  
Level 3 [Member] | Liquidity Option Agreement [Member]        
Liquidity Option Agreement [Abstract]        
Fair value inputs, Life of debt assumed after Liquidity option is exercised   30 years    
Fair value inputs, federal and state tax rate   24.00%    
Cash flow projections discount rate   7.60%    
Fair value inputs, weighted-average expected ownership percentage of contributed units at beginning of option period   89.00%    
Level 3 [Member] | Liquidity Option Agreement [Member] | Minimum [Member]        
Liquidity Option Agreement [Abstract]        
Fair value inputs, Expected life of OTA following option exercise   1 year    
Fair value inputs, Estimated growth rates in Enterprise earnings before interest, taxes, depreciation and amortization   2.10%    
Fair value inputs, OTA ownership interest in Enterprise common units   1.80%    
Level 3 [Member] | Liquidity Option Agreement [Member] | Maximum [Member]        
Liquidity Option Agreement [Abstract]        
Fair value inputs, Expected life of OTA following option exercise   30 years    
Fair value inputs, Estimated growth rates in Enterprise earnings before interest, taxes, depreciation and amortization   7.20%    
Fair value inputs, OTA ownership interest in Enterprise common units   2.50%