Credit Agreement - Narrative (Details) - Line of Credit	12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)
Line of Credit Facility [Line Items]
Defaults	$ 5,000,000.0
Weighted average interest rate	2.65%
Letters of credit	$ 34,000,000.0
Allowable indebtedness for acquisition		$ 36,000,000.0
Maximum
Line of Credit Facility [Line Items]
Total net leverage ratio	3.75
Required Minimum Value
Line of Credit Facility [Line Items]
EBITDA to fixed charges ratio	1.15
Total net leverage ratio	3.25
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility, borrowing capacity	$ 100,000,000.0
Revolving line of credit facility, outstanding	0
Line of credit facility, remaining borrowing capacity	66,000,000.0
Letter of Credit
Line of Credit Facility [Line Items]
Credit facility, borrowing capacity	$ 150,000,000.0
Maximum borrowing capacity			$ 40,000,000.0	$ 15,000,000.0