Exercise price of restricted shares granted.

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Percentage of the the authorized risk based capital requiring actions from either the entity or insurance regulators.

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This represents the total number of shares available for grant under the entity's stock incentive plan.

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Term of restrictions on stock.

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Face amount or stated value per share of common stock.

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

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For insurance companies, a description of the minimum regulatory capital requirements imposed by state insurance regulators, and restrictions on dividend payments.

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Amount of ownership interest in limited liability company (LLC) directly or indirectly attributable to noncontrolling interests.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

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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.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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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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Description of modification of award under share-based payment arrangement. Includes, but is not limited to, terms for expiration date, vesting rights and exercise price.

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Percentage of vesting of award under share-based payment arrangement.

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Amount of each item listed to reconcile the differences as of the balance sheet date resulting from applying state permitted statutory accounting practices rather than statutory accounting practices permitted by National Association of Insurance Commissioners.

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Amount of dividends that can be declared or paid without approval of regulatory agency.

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The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country.

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Stockholders' Equity and Noncontrolling Interests - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value (in usd per share)	$ 1.00			$ 1.00
Common stock, shares authorized (in shares)	50,000,000			50,000,000
Risk based capital action level percentage	200.00%
Cash dividends to common stockholders (in usd per share)	$ 0.82	$ 0.82		$ 0.82
Description of regulatory capital requirement	American National Insurance Company’s payment of dividends to stockholders is restricted by insurance law. The restrictions require life insurance companies to maintain minimum amounts of capital and surplus, and in the absence of special approval, limit the payment of dividends to the greater of the prior year’s statutory net income from operations, or 10% of prior year statutory surplus.
Noncontrolling interest	$ (6,084)			$ (6,014)
Scenario, Forecast
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Statutory amount available for dividend payments without regulatory approval					$ 347,773
Parent Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Statutory capital and surplus	3,465,660			3,477,727
Subsidiaries
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Noncontrolling equity				$ 736
Noncontrolling interest	$ 666
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk based capital action level percentage	200.00%			200.00%
Insurance Subsidiary \| Missouri
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Statutory accounting practices permitted practice amount	$ 72,979		$ 70,339
County Mutual
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Noncontrolling equity	$ 6,750			$ 6,750
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
Expiration of vesting period	5 years
Stock Appreciation Rights \| Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate per year	20.00%
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	10 years
Lapse restrictions on restricted stock awards	10 years
Shares granted (in shares)	350,334
Exercise price of Restricted shares granted	$ 0
Number of shares unvested (in shares)	10,000
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period description	RSU awards to our directors and advisory directors are settled in cash based upon the market price of our common stock after one-year or earlier upon death, disability or retirement from service after age 65.
Restricted Stock Units \| Graded Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year