Acquisitions and Divestiture (Schedule of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill, Beginning Balance	$ 745,523	$ 621,193
Goodwill, Ending Balance	790,972	745,523
FNBC Transactions [Member]
Business Acquisition [Line Items]
Goodwill, Beginning Balance	124,330
Goodwill, Ending Balance		124,330
FNBC I [Member]
Business Acquisition [Line Items]
Goodwill, Initial goodwill recorded		95,568
Goodwill, Measurement period adjustments		7,979
FNBC II [Member]
Business Acquisition [Line Items]
Goodwill, Initial goodwill recorded		23,009
Goodwill, Measurement period adjustments		$ (2,226)
Trust And Asset Management Acquisition [Member]
Business Acquisition [Line Items]
Goodwill, Initial goodwill recorded	45,634
Goodwill, Measurement period adjustments	$ (185)