Income Taxes (Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliations of the statutory federal income tax rate to our effective tax
Federal statutory rate	21.00%	21.00%	35.00%
State income taxes, net of federal benefit	4.20%	4.50%	3.00%
Change in valuation allowance	(0.40%)	(0.30%)	(0.20%)
Non-deductible expenses	1.70%	1.90%	1.80%
Uncertain tax position taxes and interest	(0.30%)	(0.50%)	0.00%
Investment tax credits	(6.50%)	(3.80%)	(1.00%)
Change in U.S. Tax Law	0.00%	0.00%	(36.20%)
Other, net	(2.60%)	(1.30%)	(2.20%)
Effective income tax rate	17.10%	21.50%	0.20%