Deferred compensation (Stock-based compensation cost) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Mar. 21, 2017	Sep. 30, 2017	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 3,112	$ 3,577		$ 3,577	$ 11,027
Less: stock-based compensation cost capitalized	(807)	(801)		(801)	(2,428)
Stock-based compensation expense	$ 2,305	$ 2,776		$ 2,776	$ 8,599
Number of vested shares repurchased	0	0		0	256,895
Payments for stock-based compensation	$ 0	$ 0		$ 0	$ 4,872
Estimated fair value per share at end of period ($ per share)	$ 17.62				$ 17.62
Aggregate intrinsic value of unvested restricted shares outstanding	$ 19,852				$ 19,852
Unrecognized stock-based compensation cost	$ 8,831				$ 8,831
Weighted-average period for unrecognized compensation cost to be recognized					11 months
Predecessor
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost			$ 194
Less: stock-based compensation cost capitalized			(39)
Stock-based compensation expense			$ 155
Number of vested shares repurchased			0
Payments for stock-based compensation			$ 0

Allocated share based compensation expense benefit.

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- Definition

Employee service share based compensation allocation of recognized period income (costs) capitalized amount.

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- Definition

Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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- Definition

Per share weighted average intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

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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.

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- Definition

Amount of capitalized and expensed compensation cost from equity-based compensation arrangements.

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- Definition

Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

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- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

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