Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 1,223,000	$ 1,333,000
Intangible assets, accumulated amortization	$ 33,672,000	$ 30,711,000
Partners’ capital:
Common units issued (in shares)	140,386,811	47,352,291
Common units outstanding (in shares)	140,386,811	47,352,291