Income Taxes (Provision For Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal, Current		$ 102,786	$ (71,878)	$ 480,446
State, Current		2,760	(7,304)	71,750
Current Foreign Tax Expense (Benefit)		19,597	0	0
Federal, Deferred		(156,767)	100,208	(127,714)
State, Deferred		28,527	(1,615)	(18,422)
Deferred Foreign Income Tax Expense (Benefit)	$ 1,400	(9,282)	0	0
Income tax provision total		$ (12,379)	$ 19,411	$ 406,060