| **Long-term Debt - Textual (Details) $ in Millions**                   |          |        |          |        |          |        | 1 Months Ended | 3 Months Ended | 9 Months Ended |        |        |
|------------------------------------------------------------------------|----------|--------|----------|--------|----------|--------|----------------|----------------|----------------|--------|--------|
||
| **Debt Instrument [Line Items]**                                       |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| Loss on early extinguishment of debt                                   |     |   |     |   |     |   |           | $ 2.6          |           |   | $ 0.0  | $ 7.4 | $ 20.0 |   |   |
| Noncurrent financing obligation liability                              |     |   |     |   |     |   |           | 281.8          |           |   |   | 281.8 |   |   | $ 288.2 |
| Development / Lease Agreement [Member]                                 |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                       |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| Initial lease term                                                     |     |   |     |   |     |   | 15 years       |           |           |   |   |   |   |   |   |
| Number of renewal options | renewal_option                             |     |   |     |   |     |   |           |           |           |   |   |   |   | 4 |   |
| Renewal term                                                           |     |   |     |   |     |   | 5 years        |           |           |   |   |   |   |   |   |
| Increase in property plant and equipment, net                          |     |   |     |   |     |   |           |           |           |   |   | 10.3 |   |   |   |
| Development / Lease Agreement [Member] | Financing Obligation [Member] |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                       |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| Total estimated financing obligation                                   |     |   |     |   |     |   |           | 56.0           |           |   |   | 56.0 |   |   |   |
| Other Notes Payable [Member] | Development / Lease Agreement [Member]  |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                       |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| Noncurrent financing obligation liability                              |     |   |     |   |     |   |           | 10.3           |           |   |   | $ 10.3 |   |   |   |
| 7.75% Senior Notes Due 2022 [Member] | Senior Notes [Member]           |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                       |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| Debt redemption price (percent)                                        | 102.583% |   | 103.875% |   | 103.875% |   |           |           |           |   |   |   |   |   |   |
| Total cash outlay upon debt redemption                                 | $ 78.0   |   | $ 52.0   |   | $ 52.0   |   |           |           |           |   |   |   |   |   |   |
| Loss on early extinguishment of debt                                   |     |   |     |   |     |   |           | $ 2.6          | $ 2.4          | $ 2.4  |   |   |   |   |   |
| Senior Notes [Member] | 7.75% Senior Notes Due 2022 [Member]           |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                       |     |   |     |   |     |   |           |           |           |   |   |   |   |   |   |
| Outstanding debt principle redeemed                                    |     | $ 76.0 |     | $ 50.0 |     | $ 50.0 |           |           |           |   |   |   |   |   |   |

| X                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of renewal options as part of the development/lease agreement for the new corporate headquarters.
+ References
No definition available.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.
+ References
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| X                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Gross amount of debt extinguished.
+ References
No definition available.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
No definition available.
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Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase (decrease) of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.
+ References
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| X                                                                                                                                                  |
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