Debt (Schedule Of Obligations Under Debt Arrangements) (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense and Discounts (Premiums)	$ 41,425,000	$ 42,946,000
Senior secured credit facility	1,280,000,000	1,115,000,000
Senior unsecured notes	1,808,575,000	1,807,054,000
Long-term debt, Face Values	3,130,000,000	2,965,000,000
Total long-term debt	3,088,575,000	2,922,054,000
6.000% senior unsecured notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense and Discounts (Premiums)	7,558,000	7,825,000
Senior unsecured notes	$ 392,442,000	$ 392,175,000
Senior unsecured notes, stated rate	6.00%	6.00%
Debt Instrument, Face Amount	$ 400,000,000	$ 400,000,000
5.750% senior unsecured notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense and Discounts (Premiums)	4,928,000	5,183,000
Senior unsecured notes	$ 345,072,000	$ 344,817,000
Senior unsecured notes, stated rate	5.75%	5.75%
Debt Instrument, Face Amount	$ 350,000,000	$ 350,000,000
5.625% senior unsecured notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense and Discounts (Premiums)	7,286,000	7,510,000
Senior unsecured notes	$ 342,714,000	$ 342,490,000
Senior unsecured notes, stated rate	5.625%	5.625%
Debt Instrument, Face Amount	$ 350,000,000	$ 350,000,000
6.75% Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense and Discounts (Premiums)	21,653,000	22,428,000
Senior unsecured notes	$ 728,347,000	$ 727,572,000
Senior unsecured notes, stated rate	6.75%	6.75%
Debt Instrument, Face Amount	$ 750,000,000	$ 750,000,000
Credit Facility [Domain]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense and Discounts (Premiums)	$ 0	$ 0

Long-term debt, Face Values before unamortized discount and debt issuance costs

No definition available.

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset. Also includes the amount of debt discount (premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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.

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
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- Definition

Carrying amount of collateralized debt obligations with maturities initially due after one year or beyond the operating cycle, if longer, excluding the current portion. Obligations include, but not limited to, mortgage loans, chattel loans, and other borrowings secured by assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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- Definition

Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
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