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-- None. No documentation exists for this element. --

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Notes At Price

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- Definition

Unamortized Debt Acquisition Costs - Contra Liability

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No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

Description of minimum financial levels (for example, tangible net worth and working capital) and achievement of certain financial ratios (for example, working capital ratio and debt service coverage ratio), and adherence to certain clauses which generally require or restrict certain actions (for example, entering into a debt arrangement with equal or greater seniority, and selling or discontinuing a certain business segment or material subsidiary) to be in compliance with the covenant clauses of the debt agreement. May also include a discussion of the adverse consequences that would result if the entity violates or fails to satisfy the covenants.

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

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

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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No definition available.

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- Definition

Represents the charge against earnings during the period for commitment fees and debt issuance expenses.

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The amount of cash paid for interest during the period.

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

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No definition available.

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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 payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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Debt (Narrative) (Details)	3 Months Ended	12 Months Ended
Debt (Narrative) (Details)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Debt Instrument [Line Items]
Unamortized Debt Acquisition Costs - Contra Liability		$ 18,672,000	$ 15,876,000
Debt Related Commitment Fees and Debt Issuance Costs			2,300,000	$ 2,400,000
Debt Instrument, Face Amount		3,400,000,000.0	2,900,000,000.0
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months		250,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Two		0
Long-term Debt, Maturities, Repayments of Principal in Year Three		250,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Four		550,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Five		280,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five		2,100,000,000
Payments of Debt Issuance Costs		6,223,000	2,912,000	4,849,000
Long-term Debt		3,458,294,000	2,982,895,000
Cash Payments for Interest		156,600,000	149,500,000	$ 134,600,000
3.20% Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 250,000,000.0	0
Debt Instrument, Interest Rate, Stated Percentage		3.20%
Long-term Debt		$ 249,700,000	0
4.20% Notes Due 2045 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 250,000,000.0	0
Debt Instrument, Interest Rate, Stated Percentage		4.20%
Long-term Debt		$ 249,914,000	0
Debt Offering Part Two [Member] \| 3.20% Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	3.20%
Notes At Price	99.871%
After Underwriting Discounts	$ 247,600,000
Payments of Debt Issuance Costs	2,100,000
Debt Offering Part Two [Member] \| 4.20% Notes Due 2045 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	4.20%
Notes At Price	99.965%
After Underwriting Discounts	$ 247,300,000
Payments of Debt Issuance Costs	$ 2,600,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		1,000,000,000
Long-term Debt		$ 279,961,000	$ 296,942,000
Commercial Paper [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Term		397 days
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Short-term Debt		$ 0
Debt Instrument, Covenant Description		The revolving credit facility described above requires us to maintain a specified ratio of consolidated debt to EBITDA (as defined in the agreement) of no greater than 5.0 to 1.0
Debt Instrument, Consolidated Debt to EBITDA Ratio		5.0
Revolving Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,000,000,000.0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.125%
Long-term Debt		$ 0
Letters of Credit Outstanding, Amount		$ 6,300,000
Revolving Credit Facility [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.625%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.275%
Revolving Credit Facility [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.10%
Line of Credit [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 250,000,000.0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.10%
Debt Instrument, Term		364 days
Line of Credit [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.625%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.225%
Line of Credit [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.08%