Income Taxes Income Taxes (Reconciliation Statutory Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%	21.00%	35.00%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	(3.20%)	(5.50%)	(2.90%)	(15.70%)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	2.30%	2.10%	2.20%	1.80%
Effective Income Tax Rate Reconciliation, Low-Income Housing and Rehabilitation, Percent	(1.20%)	0.00%	(1.10%)	0.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	2.00%	(1.30%)	1.30%	(2.10%)
Effective Income Tax Rate Reconciliation, Percent	20.90%	30.30%	20.50%	19.00%