Deferred compensation (Restricted Stock Units) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) tranche $ / shares shares	Dec. 31, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	1 year
Employee LTIP \| RSUs \| Service-condition RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	50.00%
Award vesting period (in years)	3 years
Employee LTIP \| RSUs \| Market-condition RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	50.00%
Number of tranches \| tranche	3
Employee LTIP \| Equity classified RSUs \| Service-condition RSUs
Weighted average grant date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 17.66	$ 0.00
Granted (in dollars per share) \| $ / shares	1.33	17.66
Vested (in dollars per share) \| $ / shares	17.66
Forfeited (in dollars per share) \| $ / shares	3.02	17.66
Unvested and outstanding at end of period in dollars per share) \| $ / shares	$ 2.41	$ 17.66
Restricted units
Unvested and outstanding at beginning of period (in shares) \| shares	89,633	0
Granted (in shares) \| shares	788,323	92,017
Vested (in shares) \| shares	(25,099)
Forfeited (in shares) \| shares	(214,474)	(2,384)
Unvested and outstanding at end of period (in shares) \| shares	638,383	89,633
Vest date fair value \| $	$ 33
Employee LTIP \| Equity classified RSUs \| Market-condition RSUs
Weighted average grant date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 0.00	$ 0.00
Granted (in dollars per share) \| $ / shares	1.36	0.00
Vested (in dollars per share) \| $ / shares	0.00
Forfeited (in dollars per share) \| $ / shares	1.36	0.00
Unvested and outstanding at end of period in dollars per share) \| $ / shares	$ 1.36	$ 0.00
Restricted units
Unvested and outstanding at beginning of period (in shares) \| shares	0	0
Granted (in shares) \| shares	565,000	0
Vested (in shares) \| shares	0
Forfeited (in shares) \| shares	(175,000)	0
Unvested and outstanding at end of period (in shares) \| shares	390,000	0
Employee LTIP \| Liability-classified RSUs
Weighted average grant date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 17.66	$ 0.00
Granted (in dollars per share) \| $ / shares	1.44	17.66
Vested (in dollars per share) \| $ / shares	9.33
Forfeited (in dollars per share) \| $ / shares	17.66	17.66
Unvested and outstanding at end of period in dollars per share) \| $ / shares	$ 4.57	$ 17.66
Restricted units
Unvested and outstanding at beginning of period (in shares) \| shares	37,196	0
Granted (in shares) \| shares	71,570	37,991
Vested (in shares) \| shares	(20,302)
Forfeited (in shares) \| shares	(12,685)	(795)
Unvested and outstanding at end of period (in shares) \| shares	75,779	37,196
Vest date fair value \| $	$ 25

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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.

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