Goodwill and Intangible Assets (Details Textuals) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill acquired during period	$ 3,000
Additions to finite-lived intangible assets	1,000	$ 12,000
Goodwill	971,951	968,844
Fully amortized core deposits intangibles	$ 15,000
Ahmann and Martin Company [Member]
Business Acquisition [Line Items]
Goodwill acquired during period		$ 40,000