Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
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	0	0
Preferred stock, shares outstanding	0	0
Investment securities held to maturity, fair value	$ 30,996	$ 2,201,502
Total investment securities available for sale, cost	7,052,152	4,607,117
Investments in ME securities, cost	$ 59,262	$ 73,809
Class A Common Stock
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shared authorized	16,000,000	16,000,000
Common stock, shares issued	9,624,310	10,623,220
Common stock, shares outstanding	9,624,310	10,623,220
Class B Common Stock
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shared 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
Mortgage Backed Securities
Investment securities held to maturity, fair value	$ 30,996	$ 2,201,502