Debt - Carrying Amounts of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Unamortized discount and issuance costs	$ (20.6)	$ 0.0
Total debt	359.4	0.0
Less: Current maturities	(2.7)	0.0
Total long-term debt	356.7	0.0
Notes (primarily with related parties) \| Subordinated Notes Due 2026
Debt Instrument [Line Items]
Long-term Debt	110.0	0.0
Senior Revolver \| Line of Credit
Debt Instrument [Line Items]
Long-term Debt	0.0	0.0
Senior Term Loan \| Line of Credit
Debt Instrument [Line Items]
Long-term Debt	$ 270.0	$ 0.0

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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