Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	$ 35,787	$ 24,457
Equity securities, Gross Unrealized Gains	7,650	3,446
Equity securities, Fair Value	43,437	27,903
Domestic Common Stock [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	35,787	24,457
Equity securities, Gross Unrealized Gains	7,650	3,446
Equity securities, Fair Value	$ 43,437	$ 27,903

Equity securities fair value net income gross unrealized gain.

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

+ Details

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- Definition

Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

+ References

No definition available.

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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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