Income Taxes (Reconciliation Of The Statutory Federal Income Tax With The Company's Effective Tax Rate) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components Of Income Tax Expense Benefit Continuing Operations [Abstract]
Statutory rate									$ 112,215	$ 94,338	$ 49,904
State income taxes, net of federal income tax									30,762	6,721	7,688
Foreign tax rate difference									(318)	(412)	(1,810)
Change in uncertain tax position									(617)	1,544	41
Revaluation of deferred tax assets									(3,006)	42,443
Excess tax benefit from stock-based compensation									(3,700)	(57,431)
Non-deductible litigation expense											7,700
Other, net									5,058	(538)	(2,461)
Provision for income taxes	$ 41,869	$ 36,672	$ 31,060	$ 30,793	$ 1,168	$ 41,603	$ 30,387	$ 13,507	$ 140,394	$ 86,665	$ 61,062