Number of shares issued pursuant to the terms of a deferred compensation arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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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No definition available.

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Stockholder's Equity - Long Term Incentive Plan Narrative (Detail) - Restricted Stock Units (RSUs) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted shares, vested (in shares)	806,661
Awards returned during period (in shares)	87,132
LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units ("RSUs") issued to directors and key employees (in shares)	1,078,000			1,013,000
RSU's Vested per performance criteria during period (years)	8 years
Number of restricted shares, vested (in shares)	54,755	31,036	9,958
Awards returned during period (in shares)	818,363