Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investments:
Debt securities held to maturity, fair value	$ 0	$ 7,407,703
Debt securities available for sale, amortized cost	9,874,543	3,206,120
Mortgage loans-allowance for possible losses	2,486	675
Equity securities, cost	$ 12,069	$ 16,894
Class A
STOCKHOLDERS' EQUITY (Note 12):
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	7,500,000	7,500,000
Common stock, shares issued (in shares)	3,436,020	3,436,020
Common stock, shares outstanding (in shares)	3,436,020	3,436,020
Class B
STOCKHOLDERS' EQUITY (Note 12):
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000	200,000
Common stock, shares issued (in shares)	200,000	200,000
Common stock, shares outstanding (in shares)	200,000	200,000