Income Taxes Income Taxes (Reconciliation Statutory Income Tax Rates) (Details)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	(2.60%)	9.60%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	2.20%	2.60%
Effective Income Tax Rate Reconciliation, Low-Income Housing and Rehabilitation, Percent	(1.00%)	0.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	0.60%	(0.10%)
Effective Income Tax Rate Reconciliation, Percent	20.20%	47.10%