Shares And Stockholders' Equity (Reconciliation Of The Denominator Calculations Of Basic And Diluted EPS) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
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	187,276,859	193,250,727	189,665,059	193,849,829
Shares to cover non-vested stock	1,451,686	629,997	1,239,640	644,192
Average stock options outstanding during the period	1,847,513	689,975	1,604,627	752,922
Assumed acquisition of shares with assumed proceeds and benefits from exercising stock options (at average market price for the period)	(1,444,711)	(592,887)	(1,224,255)	(588,805)
Shares repurchasable from measured but unrecognized stock option expense	(40,280)	(3,515)	(26,570)	(2,402)
Average deferred compensation shares		1,382,128		1,285,205
Weighted-average shares, as used in diluted calculation	189,091,067	195,356,425	191,258,501	195,940,941