Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Net earnings	$ 289,618	$ 264,508	$ 515,771	$ 497,277
Basic earnings per common share:
Net earnings (in dollars per basic share)	$ 2.01	$ 1.84	$ 3.58	$ 3.46
Weighted average shares outstanding - basic (in shares)	143,832,000	143,941,000	143,959,000	143,854,000
Diluted earnings per common share:
Net earnings (in dollars per diluted share)	$ 2.00	$ 1.82	$ 3.56	$ 3.43
Weighted average shares outstanding - diluted (in shares)	144,669,000	145,118,000	144,998,000	145,040,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)	143,832,000	143,941,000	143,959,000	143,854,000
Dilutive effect of assumed exercise of SAR's and vesting of performance shares (in shares)	837,000	1,177,000	1,039,000	1,186,000
Weighted average shares outstanding - diluted (in shares)	144,669,000	145,118,000	144,998,000	145,040,000
Antidilutive securities excluded from computation of earnings per share	6,000	0	32,000	34,000