Common and Subordinated Units - Per share distributions to common and subordinated unitholders (Details) - $ / shares	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Common Units
Class of Stock [Line Items]
Per unit (in usd per share)	$ 0.0800	$ 0.3700	$ 0.3800	$ 0.7400
Subordinated units
Class of Stock [Line Items]
Per unit (in usd per share)	$ 0	$ 0.3700	$ 0	$ 0.7400

Per unit of ownership amount of cash distributions paid to unit-holder of a limited partnership (LP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Name:	us-gaap_DistributionMadeToLimitedPartnerDistributionsPaidPerUnit
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration