CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Securities carried at fair value, cost	$ 4,075,406	$ 3,311,433
Allowance for Credit Losses	62	0
Estimated Fair Value	$ 101,557	$ 100,484
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	36,844,744	36,704,278
Obligations of states and political subdivisions
Allowance for Credit Losses	$ 62	$ 0
Estimated Fair Value	$ 101,557	$ 100,484
Preferred Stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	6,104	6,104
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock	$ 0	$ 0
Series A Junior Participating preferred stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	16,000	16,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock	$ 0	$ 0
Series B Fixed Rate Cumulative Perpetual Preferred Stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	81,698	81,698
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock	$ 0	$ 0
Series C Senior Non-Cumulative Perpetual Preferred Stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	81,698	81,698
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock	$ 0	$ 0
Series D Senior Non-Cumulative Perpetual Convertible Preferred Stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	3,000	3,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock	$ 0	$ 0
Series E Fixed-Rate Reset Cumulative Perpetual Preferred Stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	11,500	0
Preferred stock, shares issued (in shares)	11,500	0
Preferred stock, shares outstanding (in shares)	11,500	0
Preferred stock	$ 110,705	$ 0