Distributions To Unitholders (Details) - $ / shares	3 Months Ended						6 Months Ended	12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Dec. 31, 2017
Common units
Distribution paid per unit	$ 0.4508	$ 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	$ 0.22580
Aggregate distribution of units						184,697	310,009