Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Earnings from continuing operations	$ 168,122	$ 206,006	$ 198,085	$ 105,705	$ 157,975	$ 157,305	$ 166,456	$ 109,409	$ 677,918	$ 591,145	$ 746,663
(Loss) earnings from discontinued operations, net									0	(20,878)	65,002
Net earnings	$ 168,122	$ 206,006	$ 198,085	$ 105,705	$ 141,569	$ 157,305	$ 139,959	$ 131,434	$ 677,918	$ 570,267	$ 811,665
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 1.16	$ 1.42	$ 1.36	$ 0.73	$ 1.08	$ 1.07	$ 1.10	$ 0.71	$ 4.67	$ 3.94	$ 4.80
Earnings from discontinued operations, net (in dollars per basic share)									0	(0.14)	0.42
Net earnings (in dollars per basic share)	1.16	1.42	1.36	0.73	0.97	1.07	0.92	0.85	$ 4.67	$ 3.80	$ 5.21
Weighted average shares outstanding - basic (in shares)									145,198,000	149,874,000	155,685,000
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	1.15	1.40	1.35	0.72	1.07	1.05	1.08	0.70	$ 4.61	$ 3.89	$ 4.73
Earnings (loss) from discontinued operations, net (in dollars per diluted share)									0	(0.14)	0.41
Net earnings (in dollars per diluted share)	$ 1.15	$ 1.40	$ 1.35	$ 0.72	$ 0.96	$ 1.05	$ 0.91	$ 0.84	$ 4.61	$ 3.75	$ 5.15
Weighted average shares outstanding - diluted (in shares)									146,992,000	152,133,000	157,744,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)									145,198,000	149,874,000	155,685,000
Dilutive effect of assumed exercise of employee stock options, SAR's and performance shares (in shares)									1,794,000	2,259,000	2,059,000
Weighted average shares outstanding - diluted (in shares)									146,992,000	152,133,000	157,744,000
Weighted average number of anti-dilutive potential common shares excluded from reconciliation calculations (in shares)									28,096	1,382	79,756