Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues	$ 20,321	$ 20,154	$ 20,825	$ 21,087	$ 23,253		$ 25,770		$ 25,840		$ 25,885						$ 82,387	$ 100,748	$ 106,993
Operating expenses	8,039	8,156	7,992	8,967	7,164	[1]	9,512	[1]	10,177	[1]	10,992	[1]					33,154	37,845	42,835
Operating income	12,282	11,998	12,833	12,120	16,089		16,258		15,663		14,893						49,233	62,903	64,158
Other income (expense)	(1,967)	(1,994)	(2,219)	(2,035)	(1,990)		(1,850)		(1,791)		(1,476)						(8,215)	(7,107)	(5,171)
Income tax expense	(76)	(45)	(47)	(52)	(31)		(5)		(33)		(32)						(220)	(101)	(109)
Income (loss) from equity method investee	151	173	142	215	68		48		(117)		(13)						681	(14)	(11)
Net income	$ 10,390	$ 10,132	$ 10,709	$ 10,248	$ 14,136		$ 14,451		$ 13,722		$ 13,372						$ 41,479	55,681	$ 58,867
Quarterly distribution paid, per unit	$ 0.4750	$ 0.4750	$ 0.4750	$ 0.4750	$ 0.4750		$ 0.4750		$ 0.4750		$ 0.4750		$ 0.4700	$ 0.4600	$ 0.4500	$ 0.4400
Proceeds from the assignment of operating leases					$ 2,700													$ 2,721
Common Units [Member]
Earnings per limited partner unit (basic and diluted)	$ 0.44	$ 0.43	$ 0.45	$ 0.43	$ 0.51		0.44		0.42		0.41
Subordinated Units [Member]
Earnings per limited partner unit (basic and diluted)							$ 0.46		$ 0.42		$ 0.41

[1] Includes consideration received of $2.7 million for the assignment of railcar operating leases to Valero in the fourth quarter of 2018.