Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings from continuing operations	$ 176,279	$ 105,705
Net earnings	$ 176,279	$ 105,705
Basic earnings (loss) per common share:
Net earnings (in dollars per basic share)	$ 1.22	$ 0.73
Weighted average shares outstanding - basic (in shares)	144,259,000	145,087,000
Diluted earnings (loss) per common share:
Net earnings (in dollars per diluted share)	$ 1.21	$ 0.72
Weighted average shares outstanding - diluted (in shares)	145,782,000	146,911,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)	144,259,000	145,087,000
Dilutive effect of assumed exercise of SAR's and vesting of performance shares (in shares)	1,523,000	1,824,000
Weighted average shares outstanding - diluted (in shares)	145,782,000	146,911,000
Antidilutive securities excluded from computation of earnings per share	65,000	42,000