Fair value of financial instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Cash and cash equivalents - Book Value	$ 19,303	$ 23,354
Cash and cash equivalents - Fair Value	19,303	23,354
Restricted cash - Book Value	11,425	7,048
Restricted cash - Fair Value	11,425	7,048
Amounts due from related parties, short-term - Book Value	5,000	19,108
Amounts due from related parties, short-term - Fair Value	5,000	19,108
Loans receivable from affiliates - Book value	0	16,192
Loans receivable from affiliates - Fair Value	0	16,192
Amounts due from related parties, long-term - Book Value	0	13,757
Amounts due from related parties, long-term - Fair Value	0	13,757
Amounts due to related parties, short term - Book value	(35,979)
Amounts due to related parties, short term - Fair value	(35,979)	0
Notes receivable, net of current portion - Book Value	8,013	7,554
Notes receivable, net of current portion - Fair Value	8,013	7,554
Long-term borrowings, net - Book value	(486,857)	(489,028)
Long-term borrowings, net - Fair value	$ (491,169)	$ (494,366)

Fair value as of the balance sheet date of receivables due from all related parties.

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Fair value as of the balance sheet date of noncurrent receivables due from related parties.

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Fair value of portion of amounts due to related parties.

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Fair value of portion of loans receivable from related parties.

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The fair value of cash and cash equivalent items which are restricted as to withdrawal or usage.

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Amount of receivables arising from transactions with related parties, due after 1 year (or 1 business cycle).

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

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Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

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For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Amount, after allowance for credit loss, of financing receivable, classified as noncurrent.

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Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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