Commitments and Contingencies, Liquidity Option Agreement (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Liquidity Option Agreement [Abstract]
Liquidity option agreement	$ 275.1		$ 269.6
Change in fair value of Liquidity Option Agreement	$ 5.5	$ (2.2)
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, Assumed long-term debt	$ 2,200.0
Fair value inputs, Interest rate on assumed debt of OTA following option exercise	4.85%
Increase in fair value of liquidity option agreement excluding assumption of debt	$ 229.1
Fair value inputs, Life of debt assumed after Liquidity option is exercised	30 years
Fair value inputs, federal and state tax rate	38.00%
Cash flow projections discount rate	7.70%
Fair value inputs, weighted-average expected ownership percentage of contributed units at beginning of option period	85.00%
Increase in fair value of liquidity option agreement assuming retention of all units	$ 47.1
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	13.60%
Fair value inputs, OTA ownership interest in Enterprise common units	2.50%
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	0.10%
Fair value inputs, OTA ownership interest in Enterprise common units	1.90%