Debt and Financing - Schedule of Carrying Values and Estimated Fair Values of Debt Instruments (Details) - USD ($)
$ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
| Book Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
$ 1,225.4
|
$ 862.2
|
| Fair Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
1,226.6
|
864.7
|
| UST Loan | Book Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
349.2
|
|
| UST Loan | Fair Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
322.0
|
|
| Term Loan | Book Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
582.7
|
559.9
|
| Term Loan | Fair Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
611.0
|
559.3
|
| Lease financing obligations | Book Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
225.7
|
231.3
|
| Lease financing obligations | Fair Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
225.8
|
233.7
|
| Second A&R CDA | Book Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
67.8
|
71.0
|
| Second A&R CDA | Fair Value |
|
|
| Debt Instrument [Line Items] |
|
|
| Long-term debt, fair value |
$ 67.8
|
$ 71.7
|