Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt securities available for sale, amortized cost	$ 9,447,267	$ 9,874,543
Debt Securities, trading, amortized cost	668,285	0
Mortgage loans - allowance for possible losses	3,033	2,486
Equity securities - cost	$ 12,052	$ 12,069
Class A
STOCKHOLDERS’ EQUITY:
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:
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