Share-based Compensation - ESPP (Details) - Employee Stock Purchase Plan [Member] shares in Millions, $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($)	Jun. 30, 2018 shares
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares reserved for future issuance, in shares \| shares		2.3
Purchase election as percentage of compensation	15
Purchase price per share, as percentage of fair market value	85
Share-based compensation recognized cost \| $	$ 0.1

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section S99
-Paragraph 1
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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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.

+ References

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The percentage of eligible compensation that an employee may use to purchase stock under the plan.

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The purchase price of shares under the employee stock ownership plan, expressed as a percentage of the fair market value of the stock.

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