Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Earnings from continuing operations	$ 186,483	$ 225,683	$ 459,307	$ 606,305
Earnings (loss) from discontinued operations, net	(385)	6,161	268,697	(364)
Net earnings	$ 186,098	$ 231,844	$ 728,004	$ 605,941
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 1.20	$ 1.36	$ 2.90	$ 3.62
Earnings (loss) from discontinued operations, net (in dollars per basic share)	0.00	0.04	1.70	0.00
Net earnings (in dollars per basic share)	$ 1.20	$ 1.40	$ 4.59	$ 3.62
Weighted average shares outstanding - basic (in shares)	155,300	166,021	158,507	167,401
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	$ 1.19	$ 1.34	$ 2.87	$ 3.57
Earnings (loss) from discontinued operations, net (in dollars per diluted share)	0.00	0.04	1.68	0.00
Net earnings (in dollars per diluted share)	$ 1.19	$ 1.38	$ 4.55	$ 3.57
Weighted average shares outstanding - diluted (in shares)	156,560	168,343	160,112	169,761
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)	155,300	166,021	158,507	167,401
Dilutive effect of assumed exercise of employee stock options, SAR's and performance shares (in shares)	1,260	2,322	1,605	2,360
Weighted average shares outstanding - diluted (in shares)	156,560	168,343	160,112	169,761
Antidilutive securities excluded from computation of earnings per share	47	54	44	10