Employee Benefit Plans (Summary of the Activity in the SERP's Projected Benefit Obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Benefit obligation:
Balance, January 1	$ 96,401	$ 98,790
Service cost	3,554	4,017
Interest cost	4,103	3,703
Benefits paid	(2,565)	(2,341)
Actuarial loss (gain)	18,334	(7,768)
Balance, December 31	119,827	96,401	$ 98,790
Supplemental Executive Retirement Plan [Member]
Benefit obligation:
Balance, January 1	10,097	10,094
Service cost	97	92	143
Interest cost	408	348	360
Benefits paid	(262)	(260)	(247)
Actuarial loss (gain)	1,372	(177)
Balance, December 31	$ 11,712	$ 10,097	$ 10,094