Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Pledged securities that can be sold or repledged	$ 105,136	$ 200,339
Investment securities, available for sale, amortized cost	4,621,027	6,258,276
Investment securities, held to maturity, fair value	1,842,281	2,699,206
Equity and other securities, cost	$ 449,008	$ 487,041
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	1,000,000	1,000,000
Common stock, par value	$ 0.50	$ 0.50
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	159,741,898	159,741,898
Common stock issuable, shares	18,113	21,534
Treasury stock, common shares	31,426,742	29,174,402
Series A Series C Series And E Preferred Stock [Member]
Preferred stock, shares issued	350,000	350,000
Preferred stock, shares outstanding	350,000	350,000
Preferred stock, liquidation preference per share	$ 1,000	$ 1,000
Series F And Series G Preferred Stock [Member]
Preferred stock, shares issued	90,000	90,000
Preferred stock, shares outstanding	90,000	90,000
Preferred stock, liquidation preference per share	$ 10,000	$ 10,000