Income Taxes (Details)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Analysis of the difference between the statutory and effective tax rates from operations
U.S. federal statutory tax rate (as a percent)	35.00%	35.00%
Tax exempt interest income (as a percent)	(1.70%)	(2.10%)
Tax credits (as a percent)	(1.60%)	(0.70%)
Cash surrender value of life insurance (as a percent)	(2.00%)	(2.40%)
State income taxes (as a percent)	1.00%	1.00%
Other, net (as a percent)	0.10%
Effective tax rate (as a percent)	30.80%	30.80%