Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 02, 2019	Dec. 31, 2018
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill	$ 1,056,111			$ 1,034,679
Amortization of intangible assets	$ 3,593	$ 2,738
Customer Relationships [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets	10 years
Trade Name [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets	9 years 4 months 24 days
Core Deposits [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets	4 years 9 months 18 days
Non-Compete Agreements [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted-average remaining lives of intangible assets	9 years 7 months 6 days
First Empire [Member]
Schedule of Goodwill and Intangible Assets [Line Items]
Goodwill			$ 22,100
Weighted-average remaining lives of intangible assets	14 years 9 months 18 days