Long-Term Debt - Additional Information (Narrative) (Details) - USD ($)				3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 28, 2020	Aug. 25, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 22, 2020	Dec. 31, 2019	Jun. 23, 2017
Debt Instrument [Line Items]
Payment for Debt Extinguishment or Debt Prepayment Cost		$ 2,500,000	$ 1,700,000				$ 2,507,000	$ 1,688,000
Write-off of debt issuance costs		337,000	200,000				341,000	184,000
Debt Instrument, Repurchase Amount					$ 1,400,000
Gain (Loss) on Repurchase of Debt Instrument					$ 85,560		86,000	0
Debt Instrument, Increase, Accrued Interest			1,900,000
Debt Issuance Costs, Gross	$ 3,000,000.0			$ 3,000,000.0			3,000,000.0
Long-term debt	123,864,000			123,864,000			123,864,000			$ 149,515,000
Repayments of Secured Debt			$ 50,000,000.0				148,574,000	50,000,000
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed			25.00%
Debt Issuance Cost, Amount paid to Subsidiary	1,900,000			1,900,000			1,900,000
Debt Issuance Costs, Net	1,100,000			1,100,000			1,100,000
6.75% Senior Secured Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0	150,000,000.0		0			0			150,000,000
Long Term Debt, Amount held in Treasury		1,400,000
Interest Expense, Debt				2,400,000		$ 3,000,000.0	7,400,000	$ 9,800,000
Long Term Debt, Net Amount Outstanding		$ 148,600,000
6.75% Senior Secured Notes [Member] | Senior Secured Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount											$ 200,000,000.0
Interest rate											6.75%
Debt Instrument, Issue Price Percentage											100.00%
5.50% Senior Secured Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	125,000,000			$ 125,000,000			$ 125,000,000			$ 0
Interest Expense, Debt	$ 171,875
5.50% Senior Secured Notes | Senior Secured Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount									$ 125,000,000.0
Interest rate									5.50%