Long-term Debt - Senior Notes (Details) - Senior Notes [Member] - 4.875% Senior Unsecured Notes Due 2025 [Member] $ in Millions	9 Months Ended
Sep. 30, 2019 USD ($)
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300.0
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Debt Instrument, Maturity Date	Oct. 15, 2025
Debt Instrument, Date of First Required Payment	Apr. 15, 2018
Prior to October 15, 2020 [Member]
Debt Instrument [Line Items]
Percentage of principal that can be redeemed with cash from proceeds of an equity offering	35.00%
Debt instrument redemption price with net proceeds from equity offering	104.875%
Debt Instrument, Redemption Price, Percentage	100.00%
October 15, 2020 to October 14, 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	102.438%
October 15, 2021 to October 14, 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	101.219%
October 15, 2022 and thereafter [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	100.00%

Debt instrument redemption price with net cash proceeds of one or more equity offerings

No definition available.

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- Definition

Percentage of principal amount that can be redeemed with cash proceeds from an equity offering

+ References

No definition available.

+ Details

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- Definition

Date the debt agreement requires the first payment to be made, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

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- Definition

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

+ References

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

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

+ References

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- 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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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-Publisher FASB
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- Definition

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

+ References

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