Aggregate percentage of stock based awards to me matured.

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- Definition

Starting period of vesting of share based award.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

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- Definition

The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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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.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 718
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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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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

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- Definition

Percentage of vesting of share-based compensation awards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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Stock Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested stock options granted	$ 0	$ 0
Shares, granted (in shares)	0	0
Compensation expense restricted stock awards	$ 592,000	$ 677,000
Vested, shares (in shares)	25,940
Weighted average grant (in dollars per share)	$ 25.27
Fair value of shares vesting during period	$ 1,227,000	$ 1,462,000
Performance Based Restricted Stock Awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, granted (in shares)	16,681		15,657	7,109
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested restricted stock	$ 1,185,000
Restricted Stock Units (RSUs) \| Vested Immediately
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense restricted stock awards	$ 350,000
Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Starting period of vesting of stock based award	1 year
Aggregate percentage of stock based awards to be matured	100.00%
Key Employees \| Vesting in year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	25.00%
Key Employees \| Vesting in year two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	25.00%
Key Employees \| Vesting in year three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	25.00%
Key Employees \| Vesting in year four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	25.00%
Independent Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Starting period of vesting of stock based award	1 year
Aggregate percentage of stock based awards to be matured	100.00%
Award vesting period	3 years
Independent Directors \| Vesting in year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	33.33%
Independent Directors \| Vesting in year two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	33.33%
Independent Directors \| Vesting in year three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting per year	33.33%
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested, shares (in shares)	13,850
Weighted average grant (in dollars per share)	$ 25.27