Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investment in marketable equity securities at cost	$ 100,408	$ 59,262
Investment securities available for sale at cost	8,884,548	7,052,152
Investment securities held to maturity at fair value	$ 761,252	$ 30,996
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	345,000	0
Preferred stock, shares outstanding	345,000	0
Class A Common Stock
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized	16,000,000	16,000,000
Common stock, shares issued	8,811,220	9,624,310
Common stock, shares outstanding	8,811,220	9,624,310
Class B Common Stock
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized	2,000,000	2,000,000
Common stock, shares issued	1,005,185	1,005,185
Common stock, shares outstanding	1,005,185	1,005,185