Cash transferred 1.

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- Definition

Consolidation, Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]

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No definition available.

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- Definition

Debt Instrument Refinancing Expenses

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No definition available.

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- Definition

Interest on partial repayments of long term debt.

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No definition available.

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- Definition

Sponsor management termination fee.

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No definition available.

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- Definition

Underwriting discounts and commissions.

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No definition available.

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- Definition

Amount, after accumulated amortization, of debt premium.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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- Definition

The cash outflow associated with the repurchase of amount received from entity's first offering of stock to the public.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The cash inflow associated with the amount received from entity's first offering of stock to the public.

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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Organization - Use of the Proceeds from the IP (Detail) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidation, Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Gross proceeds	$ 631.3
Underwriters' discounts and commissions	29.2
IPO-related expenses	11.8
Redemption of 11% Senior Notes due 2021 (Note 8)	1,132.3	$ 25.9	$ 25.9	$ 11.8	$ 7.0
Sponsor management termination fee	11.3
Debt refinancing expenses	11.4
Cash to balance sheet	68.6
Senior Notes [Member] \| 11% Senior Note [Member]
Consolidation, Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Redemption of 11% Senior Notes due 2021 (Note 8)	475.0
Call premium on redemption of 11% Senior Notes due 2021	13.1
Interest on redemption of 11% Senior Notes due 2021	$ 10.9