Acquisitions (Schedule of Goodwill) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill, Beginning Balance	$ 621,193
Goodwill, Ending Balance	739,403
FNBC Transaction [Member]
Business Acquisition [Line Items]
Goodwill, Ending Balance	118,210
FNBC I [Member]
Business Acquisition [Line Items]
Goodiwll, Initial good will recorded	95,568
Goodwill, Measurement period adjustments	495
FNBC II [Member]
Business Acquisition [Line Items]
Goodiwll, Initial good will recorded	23,009
Goodwill, Measurement period adjustments	$ (862)