Supplemental Quarterly Infomation (Details) (USD $) In Thousands, except Per 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
Supplemental Quarterly Information [Abstract]
Sales and other operating revenues	$ 1,218,800		$ 1,431,000		$ 1,357,900		$ 1,281,200		$ 1,331,700		$ 1,366,500		$ 1,315,600		$ 1,298,900		$ 5,288,933		$ 5,312,686		$ 4,608,563
Income from continuing operations before income taxes	217,000		396,500		304,600		334,200		194,800		463,700		454,200		360,000		1,252,270		1,472,687		1,368,010
Income from continuing operations	442,000		271,000		142,700		169,300		180,500		265,000		259,900		182,700		1,024,973		888,137		806,494
Net income	$ 375,200		$ 245,700		$ 129,400		$ 155,300		$ 75,400		$ 284,800		$ 402,700		$ 360,600		$ 905,611		$ 1,123,473		$ 970,876
Income from continuing operations per Common share, Basic	$ 2.49		$ 1.52		$ 0.80		$ 0.94		$ 0.98		$ 1.42		$ 1.38		$ 0.96		$ 5.73		$ 4.73		$ 4.16
Income from continuing operations per Common share, Diluted	$ 2.48		$ 1.51		$ 0.79		$ 0.93		$ 0.96		$ 1.41		$ 1.37		$ 0.95		$ 5.69		$ 4.69		$ 4.14
Net income per Common share, Basic	$ 2.11		$ 1.38		$ 0.72		$ 0.86		$ 0.41		$ 1.52		$ 2.13		$ 1.89		$ 5.06		$ 5.98		$ 5.01
Net income per Common share, Diluted	$ 2.10		$ 1.37		$ 0.72		$ 0.85		$ 0.40		$ 1.51		$ 2.12		$ 1.88		$ 5.03		$ 5.94		$ 4.99
Cash dividend per Common share	$ 0.35		$ 0.35		$ 0.3125		$ 0.3125		$ 0.3125		$ 0.3125		$ 0.3125		$ 0.3125		$ 1.325		$ 1.25		$ 3.675
Market price of Common Stock, High	$ 56.13	[1]	$ 67.75	[1]	$ 66.82	[1]	$ 63.70	[1]	$ 65.55	[1]	$ 71.84	[1]	$ 66.09	[1]	$ 63.81	[1]	$ 67.75	[1]	$ 71.84	[1]
Market price of Common Stock, Low	$ 44.39	[1]	$ 56.18	[1]	$ 59.61	[1]	$ 55.68	[1]	$ 59.93	[1]	$ 59.80	[1]	$ 59.98	[1]	$ 59.33	[1]	$ 44.39	[1]	$ 59.33	[1]

[1] Prices are as quoted on the New York Stock Exchange.