Deferred compensation (Restricted Stock Awards) (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) tranche $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		1 year
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		3 years
Number of tranches \| tranche		3
Management Incentive Plan \| Time Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		3 years
Weighted average grant date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 0.00	$ 20.06	$ 20.11
Granted (in dollars per share) \| $ / shares	20.11	2.40	18.75
Vested (in dollars per share) \| $ / shares	0.00	20.08	20.12
Cancelled (in dollars per share) \| $ / shares	0.00
Forfeited (in dollars per share) \| $ / shares		20.05	20.05
Unvested and outstanding at end of period in dollars per share) \| $ / shares	$ 20.11	$ 5.41	$ 20.06
Restricted shares
Unvested and outstanding at beginning of period (in shares) \| shares	0	818,206	1,403,626
Granted (in shares) \| shares	1,403,626	886,451	41,250
Vested (in shares) \| shares	0	(408,270)	(445,029)
Cancelled (in shares) \| shares	0
Forfeited (in shares) \| shares		(226,882)	(181,641)
Unvested and outstanding at end of period (in shares) \| shares	1,403,626	1,069,505	818,206
Vest date fair value \| $		$ 2,334	$ 7,856
Management Incentive Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of tranches \| tranche		3
Weighted average grant date fair value
Unvested and outstanding at beginning of period (in dollars per share) \| $ / shares	$ 0.00	$ 20.12	$ 20.15
Granted (in dollars per share) \| $ / shares	20.12	1.38	18.75
Vested (in dollars per share) \| $ / shares	20.05	16.45	20.08
Cancelled (in dollars per share) \| $ / shares	20.05
Forfeited (in dollars per share) \| $ / shares		20.05	20.05
Unvested and outstanding at end of period in dollars per share) \| $ / shares	$ 20.15	$ 1.53	$ 20.12
Restricted shares
Unvested and outstanding at beginning of period (in shares) \| shares	0	125,528	269,473
Granted (in shares) \| shares	429,510	1,087,110	13,750
Vested (in shares) \| shares	(152,421)	(33,359)	(107,590)
Cancelled (in shares) \| shares	(7,616)
Forfeited (in shares) \| shares		(89,936)	(50,105)
Unvested and outstanding at end of period (in shares) \| shares	269,473	1,089,343	125,528
Vest date fair value \| $	$ 3,611	$ 59	$ 529

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

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No definition available.

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Share based compensation arrangement by share based payment award equity instruments other than options cancelled weighted average grant date fair value.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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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.

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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).

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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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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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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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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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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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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.

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