Debt and Credit Agreements (Details 2) (USD $)	12 Months Ended							12 Months Ended				12 Months Ended	0 Months Ended	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Senior Notes [Member] 5.75% notes due May 15, 2018	Dec. 31, 2012 Senior Notes [Member] 5.75% notes due May 15, 2018	Dec. 31, 2013 Senior Notes [Member] 5.125% notes due September 15, 2013	Dec. 31, 2012 Senior Notes [Member] 5.125% notes due September 15, 2013	Dec. 31, 2013 Senior Notes [Member] 2.7% notes due October 15, 2015	Dec. 31, 2012 Senior Notes [Member] 2.7% notes due October 15, 2015	Dec. 31, 2013 Other financing payable in varying amounts due principally through 2018 with a weighted-average interest rate of 2.7% and 9.4% at December 31, 2012 and 2011, respectively	Dec. 31, 2012 Other financing payable in varying amounts due principally through 2018 with a weighted-average interest rate of 2.7% and 9.4% at December 31, 2012 and 2011, respectively	Dec. 31, 2013 Line of credit	Sep. 12, 2013 Line of credit	Dec. 31, 2013 Line of credit	Sep. 30, 2013 Line of credit
Debt Instrument [Line Items]
Stated interest rate				5.75%	5.75%		5.125%	2.70%	2.70%
Long-term Debt	$ 803,415,000	$ 960,706,000		$ 448,268,000	$ 447,931,000	$ 0	$ 149,875,000	$ 249,373,000	$ 249,022,000	$ 105,774,000	$ 113,878,000
Less: current maturities	(20,257,000)	(3,278,000)
Total Long-term Debt	783,158,000	957,428,000
Weighted average interest rate										3.60%	2.70%
Cash payments for interest on all debt	50,100,000	45,500,000	46,400,000
Maximum proportion of subsidiary consolidated indebtedness to consolidated tangible assets												10.00%
Minimum consolidated interest coverage ratio, numerator	3.0												3.5
Minimum consolidated interest coverage ratio, denominator	1												1
Debt Instrument, Redemption Price, Percentage				5.75%				101.00%
Debt Instrument, Covenants Redemption Price as Percentage of Principal				101.00%
Debt Issuance Cost														300,000	400,000
Maturities of Long-term Debt [Abstract]
2015	267,835,000
2016	19,643,000
2017	42,667,000
2018	$ 451,860,000