Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the denominator (number of shares) in the calculations of basic and diluted earnings (loss) per common share
Weighted-average shares, as used in basic calculation	222,128,687	234,181,717	250,629,243
Shares to cover exercise of outstanding warrants	761,353	1,089,221	1,389,768
Shares to cover non-vested stock	1,626,908	1,109,490	1,302,859
Average stock options outstanding during the period	2,360,372	2,256,720	3,162,508
Assumed acquisition of shares with assumed proceeds from exercising outstanding warrants	(109,034)	(248,402)	(262,709)
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the period)	(1,414,857)	(1,508,620)	(2,258,658)
Shares repurchaseable from measured but unrecognized stock option expense	(53,241)	(49,839)	(45,958)
Average deferred compensation shares	920,792		1,021,059
Weighted-average shares, as used in diluted calculation	226,220,980	236,830,287	254,938,112