Share-Based Compensation - Restricted Stock Grants (Details) - Restricted stock units - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Trustee group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units Granted (in shares)	373,438	18,348
Grant Date Fair Value (in thousands)	$ 5,975	$ 199
Employee group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units Granted (in shares)	897,125	71,428
Vesting Period		5 years
Grant Date Fair Value (in thousands)	$ 12,677	$ 959
Minimum \| Trustee group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	1 year	2 years
Minimum \| Employee group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	2 years
Maximum \| Trustee group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years	3 years
Maximum \| Employee group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	4 years

Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Grants In Period, Grant Date Fair Value

No definition available.

+ Details

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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.

+ References

No definition available.

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