Deferred compensation (Restricted Stock Units) (Details) - Employee LTIP $ / shares in Units, $ in Thousands	6 Months Ended
Jun. 30, 2020 USD ($) $ / shares shares
Liability classified RSUs
Weighted average award date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 4.57
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	1.33
Forfeited (in dollars per share) \| $ / shares	17.66
Unvested and outstanding at end of period (in dollars per share) \| $ / shares	$ 16.83
Restricted units
Unvested and outstanding at beginning of period (in shares) \| shares	75,779
Granted (in shares) \| shares	0
Vested (in shares) \| shares	(60,000)
Forfeited (in shares) \| shares	(1,515)
Unvested and outstanding at end of period (in shares) \| shares	14,264
Vest date fair value \| $	$ 41
Service-condition \| Equity classified RSUs
Weighted average award date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 2.41
Granted (in dollars per share) \| $ / shares	1.95
Vested (in dollars per share) \| $ / shares	0
Forfeited (in dollars per share) \| $ / shares	1.56
Unvested and outstanding at end of period (in dollars per share) \| $ / shares	$ 2.87
Restricted units
Unvested and outstanding at beginning of period (in shares) \| shares	638,383
Granted (in shares) \| shares	4,500
Vested (in shares) \| shares	0
Forfeited (in shares) \| shares	(228,094)
Unvested and outstanding at end of period (in shares) \| shares	414,789
Vest date fair value \| $	$ 0
Market condition \| Equity classified RSUs
Weighted average award date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 1.36
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	0
Forfeited (in dollars per share) \| $ / shares	1.36
Unvested and outstanding at end of period (in dollars per share) \| $ / shares	$ 1.36
Restricted units
Unvested and outstanding at beginning of period (in shares) \| shares	390,000
Granted (in shares) \| shares	0
Vested (in shares) \| shares	0
Forfeited (in shares) \| shares	(200,000)
Unvested and outstanding at end of period (in shares) \| shares	190,000

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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)(1)(iv)(3)
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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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The number of grants made 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).

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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

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

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-Publisher FASB
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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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-Name Accounting Standards Codification
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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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