Line of Credit (Details)	6 Months Ended
	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Maximum ratio of total liabilities to tangible net worth	2.50
Line of Credit
Debt Instrument [Line Items]
Accordion feature allowing for increase in borrowing capacity	$ 100,000,000.0
Letters of credit outstanding amount	6,100,000
Available borrowing under letter of credit	43,900,000
Line of credit borrowings	$ 0	$ 0
EBITDA ratio	0.00
Line of Credit | Unsecured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Total availability under line of credit agreement	$ 50,000,000.0
Line of Credit | Letter of Credit
Debt Instrument [Line Items]
Available borrowing under letter of credit	$ 20,000,000.0
Minimum | Line of Credit | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate (as a percentage)	1.00%
Maximum | Line of Credit | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate (as a percentage)	1.50%