Employee Benefit Plans (Present Value of Accrued Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Executives Directors And Officer Of Acquired Entities [Member]
Present Value Of Accrued Liability [Roll Forward]
Present value of accrued liability as of January 1	$ 37,299	$ 38,597
Liability assumed in the Capital Commerce merger	808	0
Benefit expense and interest cost	535	3,262
Benefits paid	4,579	4,560
Present value of accrued liability as of December 31	34,063	37,299	$ 38,597
BancShares Plan
Present Value Of Accrued Liability [Roll Forward]
Benefit expense and interest cost	7,759	8,569	11,936
Interest cost	$ 28,376	$ 28,940	$ 28,892
Discount rate	4.38%	3.76%