Parent Company Information - Schedule of Condensed Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income
Gains on securities transactions, net	$ 524	$ (150)	$ (2,342)
Income tax (benefit) expense	139,460	147,002	68,265
Net Income	390,606	309,793	261,428
Dividends on preferred stock	12,688	12,688	12,688
Net Income Available to Common Shareholders	377,918	297,105	248,740
Parent Company
Income
Dividends from subsidiary	186,000	160,000	155,000
Income from subsidiary	4,436	4,550	4,550
Gains on securities transactions, net	0	0	3
Losses on sales of assets, net	0	0	(147)
Other interest and income	21	51	39
Total Income	190,457	164,601	159,445
Total Expenses	23,484	27,998	32,269
Income before income tax and equity in undistributed earnings of subsidiary	166,973	136,603	127,176
Income tax (benefit) expense	(3,946)	24,524	(20,547)
Income before equity in undistributed earnings of subsidiary	170,919	112,079	147,723
Equity in undistributed earnings of subsidiary	219,687	197,714	113,705
Net Income	390,606	309,793	261,428
Dividends on preferred stock	12,688	12,688	12,688
Net Income Available to Common Shareholders	$ 377,918	$ 297,105	$ 248,740