Intangible Assets (Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets [Line Items]
Impairment to goodwill		$ 0	$ 0	$ 0	$ 0
Goodwill			4,205,000	4,205,000
Additions			0	0	0
Amortization of core deposit premiums			1,422,000	1,408,000	$ 1,407,000
Unpaid principal balance of mortgage loans serviced for others			304,600,000	235,000,000
Fair value of mortgage servicing rights			2,200,000	1,700,000
Granite Corp. [Member]
Goodwill and Intangible Assets [Line Items]
Goodwill			$ 4,200,000	$ 4,200,000
CertusBank, N.A. [Member]
Goodwill and Intangible Assets [Line Items]
Bargain purchase gain	$ 300,000