Income Taxes, Major Reasons for the Difference in Effective Income Tax Rate from the Federal Tax Rate (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	(4.80%)	(5.00%)	(4.60%)
State income taxes (net of federal benefit)	2.30%	2.30%	2.80%
Bank owned life insurance	(1.70%)	(1.20%)	(1.70%)
Tax effect of tax credits and benefits, net of related expenses	(0.80%)	(0.50%)	(1.40%)
Tax reserve adjustments	0.30%	(0.60%)	0.70%
Other	0.10%	0.20%	0.20%
Effective income tax rate	30.40%	30.20%	31.00%