Income Taxes (Reconciliation Of Provision For Income Taxes) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Taxes [Abstract]
Consolidated tax provision at federal statutory rate (in hundredths)	21.00%	35.00%	21.00%	35.00%
State income tax provisions, net of federal income tax benefit (in hundredths)	0.80%	2.80%	0.40%	1.70%
Remeasurement of certain deferred tax balances			0.90%
Tax reserve adjustment (in hundredths)	0.50%	(1.00%)	0.50%	(0.20%)
Changes in certain deferred tax balances (in hundredths)	(10.40%)	7.10%	(8.60%)	0.20%
Goodwill impairment (in hundreths)	(10.40%)		(10.30%)	(10.20%)
Shared-based payments (in hundreths)		0.10%	(0.80%)	(0.20%)
Federal research and development tax credit (in hundreths)	(1.00%)	1.50%	(1.00%)	0.30%
All other, net (in hundredths)	0.40%	0.10%	0.40%	(0.10%)
Effective tax rate (in hundredths)	0.90%	45.60%	2.50%	26.50%