Employee Benefit Plans (Present Value of Accrued Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 01, 2019	Apr. 02, 2019
Present Value Of Accrued Liability [Roll Forward]
Discount rate adjustment	$ 1,719	$ 1,574
Benefit expense and interest cost	8,111	(1,582)	$ 4,572
Interest cost	$ 34,197	$ 37,260	34,733
Discount rate	2.76%	3.46%
Executives Directors And Officer Of Acquired Entities
Present Value Of Accrued Liability [Roll Forward]
Present value of accrued liability as of January 1	$ 45,295	$ 34,063
Benefit expense and interest cost	3,503	2,396
Benefits paid	7,862	4,681
Present value of accrued liability as of December 31	42,655	45,295	$ 34,063
Biscayne Bancshares
Present Value Of Accrued Liability [Roll Forward]
Liability assumed	0	1,138			$ 956,800
First South Bancorp
Present Value Of Accrued Liability [Roll Forward]
Liability assumed	0	1,067		$ 215,600
Entegra
Present Value Of Accrued Liability [Roll Forward]
Liability assumed	$ 0	$ 9,738