Debt (Consolidated Debt) (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 4,247,000,000	$ 4,100,000,000
Debt Issuance Costs, Net	(25,677,000)	(26,948,000)
Debt Instrument, Unamortized Discount (Premium), Net	4,910,000	6,530,000
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	5,679,000	7,610,000
Long-term debt, net	4,231,912,000	4,087,192,000
6.40% Notes Due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000	250,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.40%
6.55% Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000,000	550,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.55%
4.25% Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000,000	550,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.25%
3.20% Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000	250,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.20%
5.00% Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 650,000,000	650,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.00%
6.40% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000	250,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.40%
4.20% Notes Due 2042 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000	250,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.20%
5.15% Notes Due 2043 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000,000	550,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.15%
4.20% Notes Due 2045 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000	250,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.20%
4.25% Notes Due 2046 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500,000,000	500,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Commercial Paper [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 197,000,000	$ 50,000,000

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount as of the balance sheet date of the unamortized adjustment to the carrying value of an interest-bearing hedged item made under an effective interest rate fair value hedge that is amortized upon discontinuation of the interest rate fair value hedge.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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