Income Taxes (Reconciliation of Federal Statutory Rate) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Difference between the effective tax rate implicit in the consolidated financial statements and the statutory federal income tax rate
Statutory U.S. federal tax rate	21.00%	21.00%	35.00%
U.S. state income taxes, net of U.S. federal income tax effect	7.10%	5.80%	5.90%
The Tax Act	0.00%	0.10%	4.50%
Tax credits and affordable housing, net of amortization	(10.40%)	(13.30%)	(15.10%)
Other, net	2.40%	0.40%	0.90%
Effective tax rate	20.10%	14.00%	31.20%