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Shareholders' Equity - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 28, 2021	Mar. 31, 2020	Aug. 13, 2018
Shareholders' Equity [Line Items]
Authorized and unissued common shares reserved for issuance (in shares)	300,000,000	300,000,000
Common shares purchase price as percentage of fair market value	95.00%
Maximum value of shares purchased as percentage of employee compensation	10.00%
Common stock issued	$ 577	$ 567	$ 497
Share Repurchase Plan
Shareholders' Equity [Line Items]
Stock repurchase program, decrease in equity amount	$ 78,700
Share Repurchase Plan | Common Stock
Shareholders' Equity [Line Items]
Number of shares repurchased (in shares)	4,900,000
Maximum | Share Repurchase Plan | Warrant
Shareholders' Equity [Line Items]
Number of shares available for repurchase (in shares)					7,000,000.0
Maximum | Share Repurchase Plan | Warrant | Subsequent Event
Shareholders' Equity [Line Items]
Number of shares available for repurchase (in shares)				100,000,000
Dividend Reinvestment and Stock Purchase Plan
Shareholders' Equity [Line Items]
Authorized and unissued common shares reserved for issuance (in shares)	3,300,000					3,300,000
Employee Stock Purchase Plan
Shareholders' Equity [Line Items]
Number of shares available for purchase (shares)	500,000
Shares issued related to dividend reinvestment and stock purchase plan (in shares)	43,000	36,000
Common stock issued	$ 577	$ 567

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- Definition

Employee stock purchase plan maximum value of shares purchased as percentage of employee compensation.

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Employee stock purchase plan share purchase price percentage of market value.

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Shareholders' equity.

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Stock repurchase program, decrease in equity amount.

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- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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The cash inflow from the additional capital contribution to the entity.

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-Topic 230
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The highest quantity of shares an employee can purchase under the plan per period.

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-Publisher FASB
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-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Number of shares issued during the period from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the shareholders to reinvest dividends paid to them by the entity on new issues of stock by the entity.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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