Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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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 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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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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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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Stock incentive plan - Restricted stock awards (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash restricted stock unit award expense recognized	$ 2,503	$ 2,325	$ 4,834	$ 4,325
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares vested				200
Unvested restricted stock outstanding	0		0
Restricted stock awards \| Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			6,392
Restricted stock awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash restricted stock unit award expense recognized			$ 100	$ 100
Fair value of shares vested			$ 100