v3.20.4

Contract assets and contract liabilities (Tables) | 12 Months Ended
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Dec. 31, 2020
Contract assets and contract liabilities |
Schedule of contract asset, net and contract liability, net balance from customers | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Contract | ​ | Contract
​ |  | Assets, Net |  | Liabilities, Net
Balance at December 31, 2019 | ​ | $ | 967 | ​ | $ | 227,889
Balance at December 31, 2020 | ​ |  | 547 | ​ | ​ | 224,754
Change | ​ | $ | (420) | ​ | $ | (3,135)
​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at December 31, 2018 | ​ | $ | 468 | ​ | $ | 217,733
Balance at December 31, 2019 | ​ | ​ | 967 | ​ | ​ | 227,889
Change | ​ | $ | 499 | ​ | $ | 10,156
Schedule of remaining performance obligations included in revenue | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
​ |  | 2020 |  | 2019 | ​ | 2018
Amounts included in the beginning of period contract liability balance | ​ | $ | 84,368 | ​ | $ | 88,890 | ​ | $ | 85,592
Amounts associated with performance obligations satisfied in previous periods | ​ |  | (55) | ​ | ​ | 447 | ​ | ​ | 378

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- Definition Tabular disclosure of receivable, contract asset, and contract liability from contract with customer. Includes, but is not limited to, change in contract asset and contract liability. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045 + Details
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- Definition Tabular disclosure of expected timing for satisfying remaining performance obligation. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 13 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045 + Details
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