Acquisitions (Schedule of Goodwill) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill, Beginning Balance	$ 621,193
Goodwill, Ending Balance	745,523
FNBC Transaction [Member]
Business Acquisition [Line Items]
Goodwill, Ending Balance	124,330
FNBC I [Member]
Business Acquisition [Line Items]
Goodiwill, Initial goodwill recorded	95,568
Goodwill, Measurement period adjustments	7,979
FNBC II [Member]
Business Acquisition [Line Items]
Goodiwill, Initial goodwill recorded	23,009
Goodwill, Measurement period adjustments	$ (2,226)