Long-Term Debt Senior Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Senior Notes, net of unamortized deferred financing costs	$ 2,770,979	$ 2,769,663
6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount		344,611
Unamortized deferred financing costs	$ (2,483)	(2,656)
Senior Notes, net of unamortized deferred financing costs	$ 342,128	341,955
6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.125%
Senior Notes, face amount		561,796
Unamortized deferred financing costs	$ (5,505)	(5,800)
Senior Notes, net of unamortized deferred financing costs	$ 556,291	555,996
6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount		394,985
Unamortized deferred financing costs	$ (3,525)	(3,707)
Senior Notes, net of unamortized deferred financing costs	$ 391,460	391,278
5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	5.00%
Senior Notes, face amount		500,000
Unamortized deferred financing costs	$ (5,380)	(5,610)
Senior Notes, net of unamortized deferred financing costs	$ 494,620	494,390
5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	5.625%
Senior Notes, face amount		500,000
Unamortized deferred financing costs	$ (6,487)	(6,714)
Senior Notes, net of unamortized deferred financing costs	$ 493,513	493,286
6.75% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.75%
Senior Notes, face amount		500,000
Unamortized deferred financing costs	$ (7,033)	(7,242)
Senior Notes, net of unamortized deferred financing costs	492,967	492,758
Senior Notes [Member]
Debt Instrument [Line Items]
Senior Notes, face amount	2,801,392	2,801,392
Unamortized deferred financing costs	(30,413)	(31,729)
Senior Notes, net of unamortized deferred financing costs	$ 2,770,979	2,769,663
Senior Notes [Member] \| 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount	$ 344,611	344,611
Senior Notes [Member] \| 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.125%
Senior Notes, face amount	$ 561,796	561,796
Senior Notes [Member] \| 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount	$ 394,985	394,985
Senior Notes [Member] \| 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	5.00%
Senior Notes, face amount	$ 500,000	500,000
Senior Notes [Member] \| 5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	5.625%
Senior Notes, face amount	$ 500,000	500,000
Senior Notes [Member] \| 6.75% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Senior Notes, interest rate, stated percentage	6.75%
Senior Notes, face amount	$ 500,000	$ 500,000

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
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-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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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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Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

+ 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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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.

+ 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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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