Earnings (Loss) Per Common Share and Stockholders' Equity (Schedule of Earnings (Loss) Per Common Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share, Basic and Diluted [Line Items]
Net income (loss) available to common stockholders - numerator for earnings (loss) per common share	$ (65,613)	$ (253,379)	$ 206,152	$ (17,043)
Weighted average common shares outstanding (shares)	94,800,734	91,803,312	95,265,212	91,723,814
Denominator for earnings (loss) per common share - assuming dilution	95,378,663	92,026,853	95,794,584	92,023,966
Earnings (loss) per common share	$ (0.69)	$ (2.76)	$ 2.16	$ (0.19)
Earnings (loss) per common share - assuming dilution	$ (0.69)	$ (2.76)	$ 2.15	$ (0.19)
Stock Options and Deferred Compensation Agreements
Earnings Per Share, Basic and Diluted [Line Items]
Effect of dilutive securities: share-based payment arrangements (shares)	255,426	63,265	218,240	100,277
Restricted Stock and Restricted Stock Units
Earnings Per Share, Basic and Diluted [Line Items]
Effect of dilutive securities: share-based payment arrangements (shares)	322,503	160,276	311,132	199,875
Stock Options
Earnings Per Share, Basic and Diluted [Line Items]
Antidilutive securities excluded from computation of diluted earnings (loss) per common share, amount (shares)	182,689	519,285	182,689	50,000
Antidilutive securities excluded from computation of diluted earnings (loss) per common share, exercise price				$ 26.70
Stock Options | Minimum
Earnings Per Share, Basic and Diluted [Line Items]
Antidilutive securities excluded from computation of diluted earnings (loss) per common share, exercise price	$ 31.63	$ 24.79	$ 31.63
Stock Options | Maximum
Earnings Per Share, Basic and Diluted [Line Items]
Antidilutive securities excluded from computation of diluted earnings (loss) per common share, exercise price	$ 32.58	$ 26.70	$ 32.58