Premises and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premises and equipment
Total premises and equipment	$ 112,758,000	$ 108,964,000
Accumulated depreciation and amortization	(56,050,000)	(55,773,000)
Net premises and equipment	56,708,000	53,191,000
Long-lived asset impairment charges	0	150,000	$ 275,000
Depreciation and amortization of properties and equipment	5,245,000	4,780,000	$ 4,748,000
Land
Premises and equipment
Total premises and equipment	16,127,000	16,105,000
Buildings and improvements
Premises and equipment
Total premises and equipment	59,027,000	53,917,000
Furniture and equipment
Premises and equipment
Total premises and equipment	$ 37,604,000	$ 38,942,000