Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	200,608,737	215,936,448	222,128,687
Shares to cover exercise of outstanding warrants	58,765	568,602	761,353
Shares to cover non-vested stock	973,901	1,534,142	1,626,908
Average stock options outstanding during the year	1,507,049	1,739,029	2,360,372
Assumed acquisition of shares with assumed proceeds from exercising outstanding warrants	(9,594)	(81,260)	(109,034)
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the year)	(1,033,507)	(1,074,406)	(1,414,857)
Shares repurchasable from measured but unrecognized stock option expense	(217)	(14,600)	(53,241)
Average deferred compensation shares		944,151	920,792
Weighted-average shares, as used in diluted calculation	202,105,134	219,552,106	226,220,980