Distributions and Net Income Per Limited Partner Unit (Basic and Diluted Income Per Limited Partner Unit) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 16,590	$ 16,113	$ 33,181	$ 31,779
Distribution in excess of net income	(1,730)	(2,380)	(574)	(3,091)
Net income	$ 14,860	$ 13,733	$ 32,607	$ 28,688
Weighted Average Number of Limited Partnership and General Partnership Unit Outstanding, Basic and Diluted	35,194,545	35,188,189	35,194,545	33,774,647
Common units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 16,590	$ 16,113	$ 33,181	$ 31,779
Distribution in excess of net income	(1,730)	(2,380)	(574)	(3,091)
Net income	$ 14,860	$ 13,733	$ 32,607	$ 28,688
Weighted Average Number of Limited Partnership and General Partnership Unit Outstanding, Basic and Diluted	35,194,545	35,188,189	35,194,545	33,774,647
Weighted average units outsanding:
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic, Net of Tax	$ 0.43	$ 0.39	$ 0.93	$ 0.85
IDR Holders [Member]
Limited Partners' Capital Account [Line Items]
Subsequent distribution to IDR holders	$ 0	$ 0	$ 0	$ 0
Distribution in excess of net income	0	0	0	0
Net income	$ 0	$ 0	$ 0	$ 0