Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income before income taxes	$ 109,784		$ 35,792	$ 81,752	$ 63,603
Income tax expense at the U.S. federal statutory rate	(23,055)		(7,517)	(17,168)	(13,357)
State income tax expense, net of U.S. federal income tax benefit	(874)		(487)	(626)	(806)
Tax deficiencies related to stock-based compensation	(176)		(16)	(2,114)	(2,542)
Partial Release Of Valuation Allowance	(1,423)	$ 179,100	0	177,723	0
Decrease in valuation allowance due to current period activity	23,211		8,048	19,273	16,449
Other	18		(511)	8	(546)
Income tax (expense) benefit	$ (2,299)		$ (483)	$ 177,096	$ (802)