Face (par) amount of debt instrument at time of issuance.

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- Definition

Increase for accrued, but unpaid interest on the debt instrument for the period.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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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.

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- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Percentage of principal amount of debt redeemed.

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- Definition

Fair value amount of debt instrument that was repurchased.

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- Definition

Amount, after accumulated amortization, of debt premium.

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- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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- Definition

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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Debt - Issuance of 6.5% Senior Secured Notes due 2025 (Details) - USD ($)	1 Months Ended
	Nov. 30, 2017	Sep. 30, 2018	Dec. 31, 2017	Mar. 26, 2017	Dec. 25, 2016	May 31, 2014	May 14, 2014
Debt Instrument [Line Items]
Principal		$ 300,000,000	$ 300,800,000
Debt outstanding		294,000,000	$ 294,300,000
Senior notes \| 6.5% Notes
Debt Instrument [Line Items]
Stated interest rate	6.50%
Principal	$ 300,000,000
Debt issuance costs	$ 6,600,000
Debt outstanding		$ 300,000,000
Senior notes \| 6.5% Notes \| On or after November 30, 2020
Debt Instrument [Line Items]
Redemption percentage	40.00%
Percentage of principal amount	100.00%
Senior notes \| 6.5% Notes \| On or prior to November 30, 2020
Debt Instrument [Line Items]
Redemption percentage	10.00%
Percentage of principal amount	103.00%
Senior notes \| 7% Senior Notes due 2019
Debt Instrument [Line Items]
Stated interest rate		7.00%
Principal						$ 625,000,000.0
Debt issuance costs							$ 8,800,000
Reacquisition price	$ 385,200,000			$ 62,700,000	$ 14,500,000
Premium	12,000,000
Accrued interest	$ 300,000