Consolidated Statements of Changes in Partnership Capital - USD ($) shares in Thousands, $ in Thousands	General Partner [Member]	Limited Partner [Member]	Total
Balance at Dec. 31, 2018	$ 1,826	$ 84,821	$ 86,647
Balance (in shares) at Dec. 31, 2018		32,280
Net income	1,733	$ 51,032	52,765
Acquisition of assets for units	0	$ 43,824	43,824
Acquisition of assets for units (in shares)		2,400
Distributions	(2,331)	$ (68,569)	(70,900)
Balance at Dec. 31, 2019	1,228	$ 111,108	112,336
Balance (in shares) at Dec. 31, 2019		34,680
Net income	705	$ 21,162	21,867
Distributions	(1,397)	(48,242)	(49,639)
Balance at Dec. 31, 2020	$ 536	$ 84,028	$ 84,564
Balance (in shares) at Dec. 31, 2020		34,680