Pension and Other Postretirement Plans - Defined Contribution Pension Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
National Western Life Insurance Company:
Defined Benefit Plan Disclosure [Line Items]
Additional company's matching contribution	4.00%	4.00%	4.00%
Ozark National Life Insurance Company:
Defined Benefit Plan Disclosure [Line Items]
Additional company's matching contribution	4.00%
Non-Qualified Contribution Pension Plan | National Western Life Insurance Company:
Defined Benefit Plan Disclosure [Line Items]
Total company contribution, 401(k) plan	$ 143	$ 175	$ 97
Non-Qualified Contribution Pension Plan | Ozark National Life Insurance Company:
Defined Benefit Plan Disclosure [Line Items]
Expenses related to the plan	24	247	45
United States | Qualified Plan | National Western Life Insurance Company:
Defined Benefit Plan Disclosure [Line Items]
Total company contribution, 401(k) plan	755	720	664
United States | Qualified Plan | Ozark National Life Insurance Company:
Defined Benefit Plan Disclosure [Line Items]
Expenses related to the plan	125	175	176
United States | Qualified Plan | NIS
Defined Benefit Plan Disclosure [Line Items]
Expenses related to the plan	$ 10	$ 17	$ 30