Credit Facility (Details) - Line of Credit - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revolving Credit Facility
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 300,000,000.0
Possible borrowing capacity increase	150,000,000.0
Long-term debt - credit facility	$ 65,000,000.0	$ 71,800,000
Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Commitment fee percentage	0.20%
Fixed charge coverage ratio	1.25
Equity securities limitation, leverage ratio	2.75
Debt instrument, covenant, availability	$ 25,000,000.0
Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Commitment fee percentage	0.35%
Leverage ratio	3.25
Letter of Credit
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 10,000,000.0
Letters of credit outstanding	3,400,000	$ 3,200,000
Swingline Loan
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 10,000,000.0
Federal Funds Effective Swap Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.00%
LIBOR | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
LIBOR | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.75%
Base Rate | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.25%
Base Rate | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.75%