Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Preferred Stock, Par or Stated Value 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
Total investment securities available for sale, cost	$ 4,607,117	$ 7,229,014
Marketable equity securities (cost)	$ 73,809	$ 0
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	10,623,220	11,005,220
Common stock, shares outstanding	10,623,220	11,005,220
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
Debt Securities, Held-to-maturity, Fair Value	$ 2,201,502	$ 81
Total investment securities available for sale, cost	$ 2,956,793	$ 5,419,379