Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Document Fiscal Year Focus									2015
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Earnings from continuing operations	$ 136,574	$ 186,483	$ 155,634	$ 117,190	$ 171,835	$ 225,683	$ 210,581	$ 170,041	$ 595,881	$ 778,140	$ 797,527
Earnings (loss) from discontinued operations, net									273,948	(2,905)	205,602
Net earnings	$ 141,825	$ 186,098	$ 332,396	$ 209,510	$ 169,294	$ 231,844	$ 213,959	$ 160,138	$ 869,829	$ 775,235	$ 1,003,129
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 0.88	$ 1.20	$ 0.98	$ 0.72	$ 1.04	$ 1.36	$ 1.26	$ 1.00	$ 3.78	$ 4.67	$ 4.66
Earnings (loss) from discontinued operations, net (in dollars per basic share)									1.74	(0.02)	1.20
Net earnings (in dollars per basic share)	0.92	1.20	2.10	1.30	1.03	1.40	1.29	0.94	$ 5.52	$ 4.65	$ 5.86
Weighted average shares outstanding - basic (in shares)									157,619,000	166,692,000	171,271,000
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	0.87	1.19	0.97	0.72	1.03	1.34	1.25	0.99	$ 3.74	$ 4.61	$ 4.60
Earnings (loss) from discontinued operations, net (in dollars per diluted share)									1.72	(0.02)	1.18
Net earnings (in dollars per diluted share)	$ 0.91	$ 1.19	$ 2.07	$ 1.28	$ 1.02	$ 1.38	$ 1.27	$ 0.93	$ 5.46	$ 4.59	$ 5.78
Weighted average shares outstanding - diluted (in shares)									159,172,000	168,842,000	173,547,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)									157,619,000	166,692,000	171,271,000
Dilutive effect of assumed exercise of employee stock options, SAR's and performance shares (in shares)									1,553,000	2,150,000	2,276,000
Weighted average shares outstanding - diluted (in shares)									159,172,000	168,842,000	173,547,000
Weighted average number of anti-dilutive potential common shares excluded from reconciliation calculations (in shares)									25,313	38,789	0