Income Taxes, Major Reasons for the Difference in Effective Income Tax Rate from the Federal Tax Rate (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate Reconciliation
Federal income tax rate at statutory rate	35.00%	35.00%	35.00%
Increases (decreases) resulting from:
Tax-exempt interest and dividends	(5.00%)	(4.60%)	(4.50%)
State income taxes (net of federal benefit)	2.30%	2.80%	2.90%
Bank owned life insurance	(1.20%)	(1.70%)	(1.50%)
Federal tax credits	(0.50%)	(1.40%)	(1.00%)
Tax reserve adjustments	(0.60%)	0.70%	(1.90%)
Other	0.20%	0.20%	0.60%
Effective income tax rate	30.20%	31.00%	29.60%