Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
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	193,250,727	199,200,811	193,849,829	201,644,591
Shares to cover exercise of outstanding warrants		4,033		78,353
Shares to cover non-vested stock	629,997	935,823	644,192	938,920
Average stock options outstanding during the period	689,975	1,443,508	752,922	1,536,738
Assumed acquisition of shares with assumed proceeds from exercising outstanding warrants		(588)		(12,791)
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the period)	(592,887)	(988,853)	(588,805)	(1,050,065)
Shares repurchasable from measured but unrecognized stock option expense	(3,515)		(2,402)	(289)
Average deferred compensation shares	1,382,128	966,444	1,285,205
Weighted-average shares, as used in diluted calculation	195,356,425	201,561,178	195,940,941	203,135,457