Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings from continuing operations	$ 105,705	$ 109,410
Earnings (loss) from discontinued operations	0	22,025
Net earnings	$ 105,705	$ 131,435
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 0.73	$ 0.71
Earnings (loss) per share from discontinued operations (in dollars per basic share)	0	0.14
Net earnings (in dollars per basic share)	$ 0.73	$ 0.85
Weighted average shares outstanding - basic (in shares)	145,087,000	154,520,000
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	$ 0.72	$ 0.70
Earnings (loss) per share from discontinued operations (in dollars per diluted share)	0	0.14
Net earnings (in dollars per diluted share)	$ 0.72	$ 0.84
Weighted average shares outstanding - diluted (in shares)	146,911,000	157,090,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)	145,087,000	154,520,000
Dilutive effect of assumed exercise of SAR's and vesting of performance shares (in shares)	1,824,000	2,570,000
Weighted average shares outstanding - diluted (in shares)	146,911,000	157,090,000
Antidilutive securities excluded from computation of earnings per share	42,000	13,000