Long-term Debt (Tables)

12 Months Ended

Dec. 31, 2014

Long-term Debt [Abstract]

Long-term Debt

	December 31,
(Thousands of dollars)		2014	2013
Notes payable
2.50% notes, due 2017	$	550,000	550,000
3.70% notes, due 2022		600,000	600,000
4.00% notes, due 2022		500,000	500,000
7.05% notes, due 2029		250,000	250,000
5.125% notes, due 2042		350,000	350,000
Notes payable to banks, 1.4375% at December 31, 2014		450,000	350,000
Total notes payable		2,700,000	2,600,000
Unamortized discount on notes payable		(4,953)	(5,439)
Total notes payable, net of unamortized discount		2,695,047	2,594,561
Capitalized lease obligation, due through June 2028		306,579	368,251
Total debt including current maturities		3,001,626	2,962,812
Current maturities		(465,388)	(26,249)
Total long-term debt	$	2,536,238	2,936,563