Borrowing Arrangements - Narrative (Details)	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	May 31, 2019 USD ($)	Sep. 30, 2021 USD ($) $ / shares	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Feb. 16, 2021 USD ($)	May 06, 2020 USD ($)
Debt Instrument [Line Items]
Debt instrument, covenant compliance					As of September 30, 2021, the Company was in compliance with its debt covenants under the Amended Credit Agreement.
Long-term borrowings		$ 346,500,000			$ 346,500,000		$ 362,100,000
Redemptions of convertible debentures					0		0
Approximate redemption value of convertible debentures					1,100,000		1,100,000
Interest Rate Contract
Debt Instrument [Line Items]
Interest rate collar, term	3 years
Notional amount	$ 222,300,000
Interest rate collar contract maturity date	2022-04
Derivative, cap interest rate	2.50%
Liability		1,400,000			1,400,000		3,100,000
Interest rate collars paid		600,000		$ 600,000	$ 1,800,000	$ 1,000,000.0
Senior Credit Facility, Net of Discount
Debt Instrument [Line Items]
Senior credit facility maturity date					Nov. 30, 2023
Long-term borrowings		$ 322,600,000			$ 322,600,000		$ 332,300,000
Weighted average interest rate		3.60%		3.60%	3.60%	3.60%
Convertible Subordinated Debt
Debt Instrument [Line Items]
Redemption price upon stated maturity (in dollars per share) | $ / shares					$ 19.18
Redemptions stated maturity date					Apr. 01, 2028
Convertible debentures maturity per share | $ / shares		$ 25			$ 25
Amended Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity										$ 595,000,000.0
Percentage principal installments			1.875%
Amended Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 325,000,000.0	370,000,000.0
Decrease to borrowing capacity									45,000,000.0
Liquidity test minimum			$ 40,000,000.0					$ 40,000,000.0
Additional liquidity test minimum									$ 40,000,000.0
Amended Credit Agreement | Letter of Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity										100,000,000.0
Amended Credit Agreement | Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity										$ 225,000,000.0
Amended Credit Agreement | Senior Credit Facility, Net of Discount
Debt Instrument [Line Items]
Fees and other closing cost					$ 1,200,000
Letters of credit outstanding		$ 47,700,000			47,700,000
Long-term borrowings		$ 323,200,000			$ 323,200,000
Amended Credit Agreement | Senior Credit Facility, Net of Discount | Minimum
Debt Instrument [Line Items]
Fixed charge coverage ratio that is required to be maintained					2.6
Amended Credit Agreement | Senior Credit Facility, Net of Discount | Maximum
Debt Instrument [Line Items]
Total debt to EBITDA ratio that is required to be maintained		5.25
Amended Credit Agreement | Senior Credit Facility, Net of Discount | Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate		0.375%			0.375%
Amended Credit Agreement | Senior Credit Facility, Net of Discount | L I B O R Loans
Debt Instrument [Line Items]
Period of total debt to EBITDA ratio					12 months
Amended Credit Agreement | Senior Credit Facility, Net of Discount | Base Rate Loans | Federal Funds
Debt Instrument [Line Items]
Interest rate margin on variable rate basis					0.50%
Amended Credit Agreement | Senior Credit Facility, Net of Discount | Base Rate Loans | LIBOR
Debt Instrument [Line Items]
Interest rate margin on variable rate basis					2.75%
Floor interest rate					1.00%
Senior Credit Facility | Senior Credit Facility, Net of Discount
Debt Instrument [Line Items]
Weighted average interest rate		3.80%		3.80%	3.80%	3.80%