Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 27, 2019	Sep. 03, 2019	Jul. 01, 2019	Jan. 02, 2019	Dec. 31, 2018
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill	$ 1,158,123		$ 1,158,123						$ 1,034,679
Amortization of intangible assets	$ 3,800	$ 3,000	$ 10,960	$ 8,741
Customer Relationships [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets			9 years 8 months 12 days
Trade Name [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets			9 years
Core Deposits [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets			4 years 4 months 24 days
Non-Compete Agreements [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets			9 years 3 months 18 days
First Empire [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill								$ 22,700
Mooreland [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill							$ 37,400
B&F [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill						$ 19,600
GKB [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill					$ 45,200