Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	201,498,137	217,997,297	202,886,733	218,182,118
Shares to cover exercise of outstanding warrants	57,189	639,071	115,513	640,929
Shares to cover non-vested stock	831,385	1,475,976	940,471	1,534,469
Average stock options outstanding during the period	1,647,523	1,752,403	1,583,354	1,860,997
Assumed acquisition of shares with assumed proceeds from exercising outstanding warrants	(8,610)	(91,876)	(18,893)	(86,482)
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the period)	(1,119,711)	(1,086,798)	(1,080,671)	(1,094,976)
Shares repurchasable from measured but unrecognized stock option expense		(16,356)	(434)	(20,467)
Average deferred compensation shares		934,869		928,466
Weighted-average shares, as used in diluted calculation	202,905,913	221,604,586	204,426,073	221,945,054