Share-base Payment, Performance Outcome Period

No definition available.

Name:	nwli_ShareBasePaymentPerformanceOutcomePeriod
Namespace Prefix:	nwli_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Award Measurement Period

+ References

No definition available.

+ Details

Name:	nwli_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardMeasurementPeriod
Namespace Prefix:	nwli_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Vesting Price Determining Period

+ References

No definition available.

+ Details

Name:	nwli_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPriceDeterminingPeriod
Namespace Prefix:	nwli_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-Based Payment, Performance Period

+ References

No definition available.

+ Details

Name:	nwli_ShareBasedPaymentPerformancePeriod
Namespace Prefix:	nwli_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Performance Factor, Percentage Of Pre-defined Metric Target

+ References

No definition available.

+ Details

Name:	nwli_SharebasedCompensationArrangementbySharebasedPaymentAwardPerformanceFactorPercentageOfPredefinedMetricTarget
Namespace Prefix:	nwli_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Face amount or stated value per share of common stock.

+ 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
-Subparagraph (SX 210.5-02(29))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost to be recognized for option under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash inflow from exercise of option under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2A
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=SL79508275-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromStockOptionsExercised
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- 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.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529

+ Details

Name:	us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of statutory capital required to be maintained as of the balance sheet date under prescribed or permitted statutory accounting practices.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529

+ Details

Name:	us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusRequired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=nwli_EmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=nwli_EmployeeStockAppreciationRightsSARsGrantedBefore2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=nwli_ShareBasedPaymentArrangementTrancheFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=nwli_ShareBasedPaymentArrangementTrancheFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=nwli_EmployeeStockAppreciationRightsSARsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=srt_OfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=srt_DirectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=nwli_EmployeeStockOptionsandStockAppreciationRightsSARsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=nwli_IncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nwli_NationalWesternLifeInsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=nwli_ColoradoDivisionOfInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nwli_OzarkNationalLifeInsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=nwli_MissouriDepartmentOfCommerceAndInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stockholders' Equity - Regulatory Capital Requirements and Share-Based Payments - General Descriptions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, liability balance	$ 20,500,000	$ 7,900,000
Intrinsic value of share-based compensation exercised	2,600,000	4,100,000	$ 2,800,000
Fair value of options vested	7,700,000	3,700,000	4,200,000
Proceeds from exercise of stock options	$ 0	0	0
Share price (in dollars per share)	$ 281.00
Pre-tax compensation cost (benefit) recognized	$ 15,200,000	5,800,000	(2,200,000)
Compensation cost (benefit), tax expense (benefit)	(3,200,000)	(1,200,000)	500,000
Pre-tax compensation expense related to nonvested share-based awards not yet recognized	$ 27,400,000	$ 11,900,000	$ 9,100,000
Compensation cost related to nonvested options not yet recognized, weighted-average period of recognition	1 year 6 months
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Share-base payment, performance period	3 years
Performance outcome period	3 years
Award measurement period		3 years	3 years
Performance factor used to determine compensation payout		110.19%	85.16%
Employees \| Employee Stock Appreciation Rights SARs Granted Before 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requisite service period of awards	3 years
Employees \| Employee Stock Appreciation Rights SARs Granted Before 2016 \| Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Employees \| Employee Stock Appreciation Rights SARs Granted Before 2016 \| Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Employees \| Employee Stock Appreciation Rights SARs Granted Before 2016 \| Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Employees \| Employee Stock Appreciation Rights SARs Granted Before 2016 \| Tranche Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Employees \| Employee Stock Appreciation Rights SARs Granted Before 2016 \| Tranche Five
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Employees \| Employee Stock Appreciation Rights SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requisite service period of awards	1 year
Employees \| Employee Stock Appreciation Rights SARs \| Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	33.30%
Employees \| Employee Stock Appreciation Rights SARs \| Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	33.30%
Employees \| Employee Stock Appreciation Rights SARs \| Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	33.30%
Employees \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	100.00%
Award vesting period	3 years
Requisite service period of awards	3 years			3 years
Officers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant price (in dollars per share)	$ 220.61	$ 218.44
Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant price (in dollars per share)	$ 207.84	218.44
Directors \| Employee Stock Options SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requisite service period of awards	1 year
Directors \| Employee Stock Options SARs \| Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Directors \| Employee Stock Options SARs \| Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Directors \| Employee Stock Options SARs \| Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Directors \| Employee Stock Options SARs \| Tranche Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Directors \| Employee Stock Options SARs \| Tranche Five
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage	20.00%
Directors \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requisite service period of awards	1 year
Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Award vesting price determining period	20 days	20 days
Class A \| PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting price determining period	20 days
Class A \| Employees \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting price determining period	20 days
Class A \| Directors \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting price determining period	20 days
Incentive Plan \| Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value (in dollars per share)					$ 0.01
Share-based payments, number of shares authorized under plans (in shares)					300,000
National Western Life Insurance Company: \| Colorado Division of Insurance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Current authorized control level RBC	$ 118,300,000
Capital and surplus	1,700,000,000
Ozark National Life Insurance Company: \| Missouri Department of Commerce and Insurance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Current authorized control level RBC	8,100,000
Capital and surplus	$ 131,400,000