Commitments and Contingencies, Liquidity Option Agreement (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Liquidity Option Agreement [Abstract]
Liquidity Option Agreement	$ 341.4		$ 333.9
Change in fair value of Liquidity Option Agreement	$ 7.5	$ 5.5
Percentage of capital stock we agreed to purchase under liquidity option agreement	100.00%
Liquidity Option exercise period	90 days
Number of units held by limited partner	54,807,352
Liquidity Option Agreement [Member]
Liquidity Option Agreement [Abstract]
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	90.50%
Increase in fair value of liquidity option agreement assuming retention of all units	$ 35.6
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%
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%