Premises and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Premises and equipment
Total premises and equipment	$ 108,964,000	$ 103,934,000
Accumulated depreciation and amortization	(55,773,000)	(53,606,000)
Net premises and equipment	53,191,000	50,328,000
Long-lived asset impairment charges	150,000	275,000
Depreciation and amortization of properties and equipment	4,780,000	4,748,000	$ 4,727,000
Land
Premises and equipment
Total premises and equipment	16,105,000	15,785,000
Buildings and improvements
Premises and equipment
Total premises and equipment	53,917,000	51,412,000
Furniture and equipment
Premises and equipment
Total premises and equipment	$ 38,942,000	$ 36,737,000