Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of information used in computing basic and diluted earnings per share [Abstract]
Earnings from continuing operations	$ 171,835	$ 225,683	$ 210,581	$ 170,041	$ 172,227	$ 217,045	$ 247,988	$ 160,267	$ 778,140	$ 797,527	$ 650,075
(Loss) earnings from discontinued operations, net									(2,905)	205,602	160,995
Net earnings	$ 169,294	$ 231,844	$ 213,959	$ 160,138	$ 193,963	$ 269,114	$ 330,049	$ 210,003	$ 775,235	$ 1,003,129	$ 811,070
Basic earnings (loss) per common share:
Earnings from continuing operations (in dollars per basic share)	$ 1.04	$ 1.36	$ 1.26	$ 1.00	$ 1.01	$ 1.27	$ 1.45	$ 0.92	$ 4.67	$ 4.66	$ 3.58
Earnings (loss) from discontinued operations, net (in dollars per basic share)									$ (0.02)	$ 1.20	$ 0.89
Net earnings (in dollars per basic share)	$ 1.03	$ 1.40	$ 1.29	$ 0.94	$ 1.14	$ 1.58	$ 1.93	$ 1.21	$ 4.65	$ 5.86	$ 4.47
Weighted average shares outstanding - basic (in shares)									166,692,000	171,271,000	181,551,000
Diluted earnings (loss) per common share:
Earnings from continuing operations (in dollars per diluted share)	$ 1.03	$ 1.34	$ 1.25	$ 0.99	$ 1.00	$ 1.26	$ 1.43	$ 0.91	$ 4.61	$ 4.60	$ 3.53
Earnings (loss) from discontinued operations, net (in dollars per diluted share)									$ (0.02)	$ 1.18	$ 0.88
Net earnings (in dollars per diluted share)	$ 1.02	$ 1.38	$ 1.27	$ 0.93	$ 1.13	$ 1.56	$ 1.91	$ 1.20	$ 4.59	$ 5.78	$ 4.41
Weighted average shares outstanding - diluted (in shares)									168,842,000	173,547,000	183,993,000
Reconciliation Of Share Amounts Used In Computing Earnings Per Share [Abstract]
Weighted average shares outstanding - basic (in shares)									166,692,000	171,271,000	181,551,000
Dilutive effect of assumed exercise of employee stock options, SAR's and performance shares (in shares)									2,150,000	2,276,000	2,442,000
Weighted average shares outstanding - diluted (in shares)									168,842,000	173,547,000	183,993,000
Weighted average number of anti-dilutive potential common shares excluded from reconciliation calculations (in shares)									38,789	0	0