Summary of Significant Accounting Policies - Restricted Cash and Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Restricted cash
Restricted cash	$ 0	$ 958
Accounts Receivable [Abstract]
Allowance for credit losses	400	2,600
Retainage	36,230	$ 42,547
Retainage, long-term	$ 7,200

Amount of allowance for credit loss on accounts receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract.

+ References

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-Publisher FASB
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Balance Type:	debit
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- Definition

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract to be collected after the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Balance Type:	debit
Period Type:	instant

- References

No definition available.

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Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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Period Type:	duration

- Definition

Amount of cash restricted as to withdrawal or usage, classified as current. 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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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