Equity Incentive Plan - Expense per performance share award (Details)	3 Months Ended
Mar. 31, 2020 $ / shares
June 3, 2019 \| Performance share awards with market criteria
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	$ 2.45
Expense per performance share award (USD per share)	2.45
June 3, 2019 \| Performance share awards with performance criteria
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	2.59
Expense per performance share award (USD per share)	$ 4.53
Estimated payout for expense (as a percent)	175.00%
June 3, 2019 \| Performance share awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	$ 2.52
Expense per performance share award (USD per share)	3.49
February 28, 2019 \| Performance share awards with market criteria
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	3.98
Expense per performance share award (USD per share)	3.98
February 28, 2019 \| Performance share awards with performance criteria
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	3.49
Expense per performance share award (USD per share)	$ 6.11
Estimated payout for expense (as a percent)	175.00%
February 28, 2019 \| Performance share awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	$ 3.74
Expense per performance share award (USD per share)	5.05
February 16, 2018 \| Performance share awards with market criteria
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	10.08
Expense per performance share award (USD per share)	10.08
February 16, 2018 \| Performance share awards with performance criteria
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	8.36
Expense per performance share award (USD per share)	$ 6.27
Estimated payout for expense (as a percent)	75.00%
February 16, 2018 \| Performance share awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per performance share award (USD per share)	$ 9.22
Expense per performance share award (USD per share)	$ 8.18

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- Definition

Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Grants In Period, Expense Per Performance Share Award

+ References

No definition available.

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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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

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