Income Taxes (Reconciliation Of Provision For Income Taxes) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Taxes [Abstract]
Consolidated tax provision at federal statutory rate (in hundredths)	35.00%	35.00%	35.00%	35.00%
State income tax provisions, net of federal income tax benefit (in hundredths)	4.20%	31.40%	4.30%	7.80%
Tax reserve adjustment (in hundredths)	6.30%	(15.90%)	0.70%	(3.70%)
Domestic production activities deduction (in hundreths)	(9.50%)	15.80%	(2.40%)	3.60%
Changes in certain deferred tax balances (in hundredths)	(0.80%)	(9.50%)	3.10%	6.20%
Federal research and development tax credit (in hundreths)	1.50%	5.40%	1.20%	1.10%
All other, net (in hundredths)		0.90%	0.10%	(0.30%)
Effective tax rate (in hundredths)	36.70%	63.10%	42.00%	49.70%