Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 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	215,901,268	220,813,693	217,413,480	223,311,993
Shares to cover exercise of outstanding warrants	579,882	668,103	620,580	795,312
Shares to cover non-vested stock	1,467,953	1,614,405	1,512,297	1,572,250
Average stock options outstanding during the period	1,700,026	2,275,826	1,807,340	2,432,171
Assumed acquisition of shares with assumed proceeds from exercising outstanding warrants	(86,040)	(94,338)	(86,335)	(116,577)
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the period)	(1,082,651)	(1,361,094)	(1,090,868)	(1,481,524)
Shares repurchasable from measured but unrecognized stock option expense	(11,209)	(44,579)	(17,381)	(60,539)
Average deferred compensation shares			936,355	926,612
Weighted-average shares, as used in diluted calculation	218,469,229	223,872,016	221,095,468	227,379,698