Debt and Financing Arrangements (Details) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 15, 2018
Debt Instrument [Line Items]
Proceeds from borrowings on Credit Agreement				$ 75,000,000	$ 0	$ 0
Repayment of borrowings on Credit Agreement				75,000,000	0	$ 78,000,000
Revolver
Debt Instrument [Line Items]
Principal amount							$ 150,000,000
Additional principal amount available (up to)							100,000,000
Proceeds from borrowings on Credit Agreement			$ 75,000,000
Repayment of borrowings on Credit Agreement	$ 25,000,000	$ 50,000,000
Interest expense				600,000
Amount outstanding	$ 0			$ 0	$ 0
Swing loans
Debt Instrument [Line Items]
Additional principal amount available (up to)							20,000,000
Letters of Credit
Debt Instrument [Line Items]
Additional principal amount available (up to)							$ 20,000,000