Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt securities held to maturity, allowance for expected credit losses	$ 5,086	$ 0
Debt securities held to maturity - fair value	7,378,399	7,407,703
Debt securities available for sale, amortized cost	3,156,486	3,206,120
Mortgage loans - allowance for possible losses	2,357	675
Equity securities - cost	$ 15,157	$ 16,894
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