Notes Payable and Credit Agreement - Letters of Credit (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding	$ 24,064	$ 19,752
Debt collateral	2,154
Senior Credit Facility \| Line of Credit
Line of Credit Facility [Line Items]
Debt collateral	$ 21,910

Amount of assets pledged to secure a debt instrument.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Name:	us-gaap_DebtInstrumentCollateralAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant