Employee Incentive Plans - Restricted and Performance Awards (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended		9 Months Ended
	Jul. 31, 2020	Mar. 31, 2020	Feb. 29, 2020	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Grant-Date Fair Value (in dollars per share)	$ 2.33	$ 1.13		$ 7.69
Beginning TSR Price (in dollars per share)	$ 2.52	$ 1.25		$ 6.13
Risk-free interest rate	0.17%	0.42%		1.62%
Volatility factor	67.00%	51.00%		37.00%
Unvested restricted units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning of period (in shares)				4,063,605			4,063,605
Granted (in shares)			1,144,842				4,873,848
Vested (in shares)							(2,839,869)
Forfeited (in shares)							(661,623)
Non-vested, end of period (in shares)					5,435,961		5,435,961
Aggregate intrinsic value, end of period					$ 12.8		$ 12.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested, beginning of period (in dollars per share)				$ 13.85			$ 13.85
Granted (in dollars per share)							5.42
Vested (in dollars per share)							10.93
Forfeited (in dollars per share)							8.28
Non-vested, end of period (in dollars per share)					$ 8.50		$ 8.50
Incentive unit award vesting period							3 years
Fair value of units vested			$ 5.2
Units withheld for payroll taxes (in shares)							1,009,546
Unrecognized compensation cost related to non-vested restricted incentive units					$ 23.3		$ 23.3
Unrecognized compensation costs, weighted average period for recognition							1 year 7 months 6 days
Unvested restricted units | ENLC
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value of units vested					6.0	$ 5.8	$ 31.0	$ 18.9
Aggregate intrinsic value of units vested					$ 1.0	3.1	$ 11.9	16.0
Performance units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning of period (in shares)				1,317,856			1,317,856
Granted (in shares)							1,361,986
Vested (in shares)							(181,647)
Forfeited (in shares)							(166,211)
Non-vested, end of period (in shares)					2,331,984		2,331,984
Aggregate intrinsic value, end of period					$ 5.5		$ 5.5
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested, beginning of period (in dollars per share)				$ 14.22			$ 14.22
Granted (in dollars per share)							6.63
Vested (in dollars per share)							30.31
Forfeited (in dollars per share)							11.01
Non-vested, end of period (in dollars per share)					$ 8.76		$ 8.76
Fair value of units vested					$ 0.0	6.0	$ 5.5	7.9
Units withheld for payroll taxes (in shares)							69,052
Aggregate intrinsic value of units vested					0.0	$ 1.6	$ 0.9	$ 3.4
Unrecognized compensation cost related to non-vested restricted incentive units					$ 12.3		$ 12.3
Unrecognized compensation costs, weighted average period for recognition							1 year 6 months
Performance units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Percent of units vesting							0.00%
Performance units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Percent of units vesting							200.00%