Income Taxes (Reconciliation Of Provision For Income Taxes) (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Taxes [Abstract]
Consolidated tax provision at federal statutory rate (in hundredths)	21.00%	21.00%
State income tax provisions, net of federal income tax benefit (in hundredths)	(3.20%)	7.20%
Remeasurement of certain deferred tax balances		(11.90%)
Tax reserve adjustment (in hundredths)	(0.90%)	1.20%
Changes in certain deferred tax balances (in hundredths)	(38.60%)	14.20%
Shared-based payments (in hundreths)	(4.40%)	10.60%
Federal research and development tax credit (in hundreths)	1.70%	(2.00%)
All other, net (in hundredths)	(1.60%)	0.80%
Effective tax rate (in hundredths)	(26.00%)	41.10%