Stockholders' Equity - Dividend Restrictions (Details) - USD ($)			3 Months Ended		12 Months Ended
	Oct. 30, 2020	Jan. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class A
Class of Stock [Line Items]
Dividends declared and paid					$ 1,237,000	$ 1,237,000	$ 1,237,000
Class B
Class of Stock [Line Items]
Dividends declared and paid					36,000	$ 36,000	$ 36,000
National Western Life Insurance Company:
Class of Stock [Line Items]
Maximum dividend payment which may be paid without prior approval					45,500,000
Dividends declared and paid				$ 32,000,000.0	0
National Western Life Insurance Company: | Dividend Declared
Class of Stock [Line Items]
Dividends declared and paid			$ 4,000,000.0
Ozark National Life Insurance Company:
Class of Stock [Line Items]
Maximum dividend payment which may be paid without prior approval					21,000,000.0
Extraordinary dividend paid		$ 102,700,000
NIS
Class of Stock [Line Items]
Maximum dividend payment					$ 4,500,000
National Western Life Group Inc | Class A
Class of Stock [Line Items]
Common stock, dividends declared (in dollars per share)	$ 0.36
National Western Life Group Inc | Class B
Class of Stock [Line Items]
Common stock, dividends declared (in dollars per share)	$ 0.18