The number of units of other ownership interests vested.

No definition available.

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- Definition

Represents the percentage of amount of equity value in excess of threshold limit for conversion of units to common shares.

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No definition available.

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- Definition

Represents the percentage of amount of quarterly distribution in excess of threshold limit.

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No definition available.

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- Definition

Represents the percentage of newly issued common shares to the total number of issued and outstanding common shares allowed.

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No definition available.

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Estimated value relating to share-based payment award.

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No definition available.

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- Definition

Floor equity value relating to share-based payment award.

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No definition available.

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- Definition

Weighted average cost of capital relating to the share-based payment award.

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No definition available.

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- Definition

Represents the amount of threshold limit for conversion of units to common shares.

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No definition available.

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Represents the amount of threshold limit for quarterly distribution.

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No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Aggregate number of common shares reserved for future issuance.

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Maximum number of common units of ownership permitted to be issued by a limited liability company (LLC).

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No definition available.

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Number of common units of ownership outstanding of a limited liability company (LLC).

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No definition available.

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No definition available.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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- Definition

Gross number of share options (or share units) granted during the period.

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No definition available.

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Long-Term Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		17 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017	Apr. 17, 2017
Aggregate disclosure
Units vested	32,875		32,875		32,875	32,875
2017 LTIP
Aggregate disclosure
Expense recognized	$ 0.2	$ 0.1	$ 0.5	$ 0.1
Number of common shares may be delivered pursuant to awards, subject to customary adjustments							930,851
Awards granted					39,156
Remaining shares granted	891,695		891,695		891,695
IDR LLC
Long-Term Incentive Plan
Percentage of amount of quarterly distribution in excess of threshold limit			6.00%
Threshold limit for quarterly distribution			$ 7.5
Aggregate disclosure
Units vested	32,875		32,875		32,875
IDR LLC \| Series B unit awards
Long-Term Incentive Plan
Authorized units	98,600		98,600		98,600
Outstanding units	98,600		98,600		98,600
Threshold limit for quarterly distribution			$ 7.5
Threshold limit for conversion of units to common shares	$ 2,000.0		$ 2,000.0		$ 2,000.0
Assumptions:
Vesting period			3 years
Aggregate disclosure
Expense recognized	8.4	8.2	$ 25.8	26.2
Unamortized compensation expense related to nonvested Series B units	43.0		$ 43.0		43.0
Weighted average period for recognizing unrecognized stock-based compensation expense			1 year 3 months
IDR LLC \| Series B unit awards \| Maximum
Long-Term Incentive Plan
Percentage of amount of quarterly distribution in excess of threshold limit			6.00%
Percentage of amount of equity value in excess of threshold limit for conversion of units to common shares			6.00%
Percentage of newly issued common shares to the total number of issued and outstanding common shares allowed			6.00%
IDR LLC \| Series B Unit Awards classified as equity
Assumptions:
Floor equity value	2,000.0		$ 2,000.0		2,000.0
Vesting period			10 years
Expected volatility (as a percent)			43.00%
Risk free rate (as a percent)			2.45%
Weighted average cost of capital (as a percent)			7.25%
Estimated value (in dollars per unit)			$ 999
Aggregate disclosure
Expense recognized	7.6	7.6	$ 22.8	22.9
Awards granted			92,000
Awards forfeited			500
IDR LLC \| Series B Unit Awards classified as liability
Assumptions:
Floor equity value	3,300.0		$ 3,300.0		$ 3,300.0
Expected volatility (as a percent)			38.00%
Risk free rate (as a percent)			3.00%
Weighted average cost of capital (as a percent)			7.25%
Estimated value (in dollars per unit)			$ 1,673
Aggregate disclosure
Expense recognized	$ 0.8	$ 0.6	$ 3.0	$ 3.3
Awards granted			8,000
Awards forfeited			900