Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Earnings from continuing operations	$ 99,356	$ 117,190
Earnings from discontinued operations, net	0	92,320
Net earnings	$ 99,356	$ 209,510
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 0.64	$ 0.72
Earnings from discontinued operations, net (in dollars per basic share)	0.00	0.57
Net earnings (in dollars per basic share)	$ 0.64	$ 1.30
Weighted average shares outstanding - basic (in shares)	155,064,000	161,650,000
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	$ 0.64	$ 0.72
Earnings from discontinued operations, net (in dollars per diluted share)	0.00	0.57
Net earnings (in dollars per diluted share)	$ 0.64	$ 1.28
Weighted average shares outstanding - diluted (in shares)	156,161,000	163,323,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)	155,064,000	161,650,000
Dilutive effect of assumed exercise of employee stock options, SAR's and performance shares (in shares)	1,097,000	1,673,000
Weighted average shares outstanding - diluted (in shares)	156,161,000	163,323,000
Antidilutive securities excluded from computation of earnings per share	27,000	56,000