Long-Term Debt - Additional Information (Narrative) (Details) - USD ($)				3 Months Ended		12 Months Ended
	Sep. 28, 2020	Aug. 25, 2019	Jun. 23, 2017	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 22, 2020
Debt Instrument [Line Items]
Debt Issuance Costs, Gross				$ 3,100,000		$ 3,100,000
Payment for Debt Extinguishment or Debt Prepayment Cost	$ 2,500,000
Write-off of debt issuance costs	341,200					341,000	$ 184,000	$ 0
Long Term Debt, Net Amount Outstanding	148,600,000
Debt issuance cost, Amount paid to Subsidiary				1,900,000		1,900,000
Debt Issuance Costs, Net				1,200,000		1,200,000
Gain (Loss) on Repurchase of Debt Instrument						(86,000)
6.75% Senior Secured Notes [Member]
Debt Instrument [Line Items]
Interest Paid Long Term Debt						7,400,000	12,300,000
Long-term Debt, Gross	150,000,000.0
Long Term Debt, Amount held in Treasury	1,400,000
Long Term Debt, Net Amount Outstanding	$ 148,600,000
Interest Expense, Debt						7,400,000	12,300,000	$ 13,500,000
Debt Instrument, Repurchase Amount					$ 1,400,000
Gain (Loss) on Repurchase of Debt Instrument					$ 85,560
6.75% Senior Secured Notes [Member] | Senior Secured Notes
Debt Instrument [Line Items]
Private placement date			Jun. 23, 2017
Debt Instrument, Face Amount			$ 200,000,000.0
Interest rate			6.75%
Debt Instrument, Redemption Price, Percentage	101.6875%	25.00%
Debt Instrument, Issue Price Percentage			100.00%
Repayments of Secured Debt		$ 50,000,000.0
Total Debt Redemption Costs on 25% Note Redemption		1,900,000
Payment for Debt Extinguishment or Debt Prepayment Cost		1,700,000
Write-off of debt issuance costs		$ 200,000
Long-term Debt, Gross							150,000,000
5.50% Senior Secured Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				125,000,000		$ 125,000,000	$ 0
Interest Expense, Debt				$ 1,900,000
5.50% Senior Secured Notes [Member] | Senior Secured Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount									$ 125,000,000.0
Interest rate									5.50%