Long-term Debt - Schedule of Long-term Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Obligations under finance leases	$ 57,300,000
Obligations under finance leases		$ 26,200,000
Total long-term debt	382,100,000	346,200,000
Outstanding letters of credit	16,700,000
Unused credit facility and letter of credit participation	1,200,000	1,200,000	$ 1,000,000.0
Charges related to amortization of debt issuance costs	800,000	800,000	$ 800,000
Revolving Credit Facility | Minimum
Debt Instrument [Line Items]
Average borrowings	141,700,000	175,000,000
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Average borrowings	508,000,000	575,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Amounts borrowed (Credit Facility)	324,800,000	320,000,000.0
Outstanding letters of credit	16,700,000	16,700,000
Amounts available to borrow	341,700,000	328,900,000
Average borrowings	303,200,000	336,800,000
Unamortized debt issuance costs	$ 1,700,000	$ 2,500,000
Weighted-average interest rate (percent)	3.40%	3.10%
Revolving credit facility, expansion feature	$ 200,000,000.0