Distributions To Unitholders (Details) - $ / shares		3 Months Ended					12 Months Ended
	May 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Common units
Distribution paid per unit		$ 0.4508	$ 0.4508	$ 0.4508	$ 0.4441	$ 0.4375
Aggregate distribution of units							393,291
Class B preferred units
Distribution paid per unit		$ 0.28225	$ 0.28225	$ 0.28225	$ 0.28225	$ 0.2258
Aggregate distribution of units	184,697