Employees, Retirement and Incentive Plans Restricted Units (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Restricted and Phantom Units
Share-based Compensation Arrangements
Nonvested restricted units outstanding	137,541	145,205
Vesting and transfer of common units to recipients	4,397
Vested in Period	$ 30.29
Weighted average grant date fair value	$ 26.14	$ 26.22
Forfeitures	3,267
Weighted Average Grant Date Fair Value - Forfeitures	$ 24.44
Total unrecognized compensation related to nonvested units	$ 1.9
Weighted average remaining contractual term (years)	1 year 4 months 24 days
Performance Shares [Member]
Share-based Compensation Arrangements
Nonvested restricted units outstanding	41,811	53,445
Vesting and transfer of common units to recipients	11,634
Total unrecognized compensation related to nonvested units	$ 0.5
Weighted average remaining contractual term (years)	1 year 9 months 18 days

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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-Publisher FASB
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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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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Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event.

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