Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Earnings from continuing operations	$ 118,290	$ 155,634	$ 217,646	$ 272,824
Earnings from discontinued operations, net	0	176,762	0	269,082
Net earnings	$ 118,290	$ 332,396	$ 217,646	$ 541,906
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 0.76	$ 0.98	$ 1.40	$ 1.70
Earnings from discontinued operations, net (in dollars per basic share)	0.00	1.11	0.00	1.68
Net earnings (in dollars per basic share)	$ 0.76	$ 2.10	$ 1.40	$ 3.38
Weighted average shares outstanding - basic (in shares)	155,180,000	158,640,000	155,122,000	160,137,000
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	$ 0.76	$ 0.97	$ 1.39	$ 1.69
Earnings from discontinued operations, net (in dollars per diluted share)	0.00	1.10	0.00	1.66
Net earnings (in dollars per diluted share)	$ 0.76	$ 2.07	$ 1.39	$ 3.35
Weighted average shares outstanding - diluted (in shares)	156,595,000	160,398,000	156,414,000	161,876,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)	155,180,000	158,640,000	155,122,000	160,137,000
Dilutive effect of assumed exercise of employee stock options, SAR's and performance shares (in shares)	1,415,000	1,758,000	1,292,000	1,739,000
Weighted average shares outstanding - diluted (in shares)	156,595,000	160,398,000	156,414,000	161,876,000
Antidilutive securities excluded from computation of earnings per share	60,000	45,000	65,000	35,000