Long term Debt (Schedule of Long Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Notes payable	$ 2,700,000us-gaap_DebtInstrumentCarryingAmount	$ 2,600,000us-gaap_DebtInstrumentCarryingAmount
Unamortized discount on notes payable	(4,953)	(5,439)
Total notes payable, net of unamortized discount	2,695,047us-gaap_LongTermDebt	2,594,561us-gaap_LongTermDebt
Capitalized lease obligation, due through June 2028	306,579us-gaap_CapitalLeaseObligations	368,251us-gaap_CapitalLeaseObligations
Total debt including current maturities	3,001,626us-gaap_DebtAndCapitalLeaseObligations	2,962,812us-gaap_DebtAndCapitalLeaseObligations
Current maturities	(465,388)	(26,249)
Total long-term debt	2,536,238	2,936,563
2.50% notes, due 2017 [Member]
Debt Instrument [Line Items]
Notes payable	550,000	550,000
Notes payable, stated interest rate	2.50%	2.50%
Notes payable, due date	2017	2017
3.70% notes, due 2022 [Member]
Debt Instrument [Line Items]
Notes payable	600,000	600,000
Notes payable, stated interest rate	3.70%	3.70%
Notes payable, due date	2022	2022
4.00% notes, due 2022 [Member]
Debt Instrument [Line Items]
Notes payable	500,000	500,000
Notes payable, stated interest rate	4.00%	4.00%
Notes payable, due date	2022	2022
7.05% notes, due 2029 [Member]
Debt Instrument [Line Items]
Notes payable	250,000	250,000
Notes payable, stated interest rate	7.05%	7.05%
Notes payable, due date	2029	2029
5.125% notes, due 2042 [Member]
Debt Instrument [Line Items]
Notes payable	350,000	350,000
Notes payable, stated interest rate	5.125%	5.125%
Notes payable, due date	2042	2042
Notes payable to banks, 1.4375% [Member]
Debt Instrument [Line Items]
Notes payable	$ 450,000	$ 350,000
Notes payable, stated interest rate	1.4375%

Debt Instrument Maturity Year

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- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

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-Publisher FASB

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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

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