Business Combinations (Schedule of Goodwill) (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill, Beginning Balance	$ 855,453,000	$ 790,972,000
Goodwill, Ending Balance	855,453,000	855,453,000
MidSouth [Member]
Business Acquisition [Line Items]
Goodwill, Initial goodwill recorded		69,207,000
Goodwill, Measurement period adjustments	0	(5,838,000)
Goodwill, Ending Balance	$ 63,369,000
Trust and Asset Management Business [Member]
Business Acquisition [Line Items]
Final settlement of cash consideration - acquisition of trust and asset management business		$ 1,112,000