Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
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		199,200,811	215,901,268	201,644,591	217,413,480
Shares to cover exercise of outstanding warrants		4,033	579,882	78,353	620,580
Shares to cover non-vested stock		935,823	1,467,953	938,920	1,512,297
Average stock options outstanding during the period		1,443,508	1,700,026	1,536,738	1,807,340
Assumed acquisition of shares with assumed proceeds from exercising outstanding warrants		(588)	(86,040)	(12,791)	(86,335)
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the period)		(988,853)	(1,082,651)	(1,050,065)	(1,090,868)
Shares repurchasable from measured but unrecognized stock option expense			(11,209)	(289)	(17,381)
Average deferred compensation shares		966,444			936,355
Weighted-average shares, as used in diluted calculation	[1]	201,561,178	218,469,229	203,135,457	221,095,468

[1] Due to reporting a net loss for the three months ended September 30, 2019, basic shares were used in the diluted earnings per share (“EPS”) calculation for that period as the use of diluted shares would have resulted in a lower loss per share.