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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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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Amount of interest capitalized during the period.

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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.

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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.

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Senior Notes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Senior Notes (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Senior Notes [Line Items]
Principal Amount, Net of Unamortized Deferred Financing Costs	$ 2,450,737		$ 2,450,737		$ 2,448,439
Interest Costs Capitalized	$ 5,000	$ 6,000	$ 9,900	$ 10,500
6.125% Senior Notes due 2022 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage	6.125%		6.125%
Principal Amount	$ 476,796		$ 476,796		476,796
Unamortized Deferred Financing Costs	(3,420)		(3,420)		(3,921)
Principal Amount, Net of Unamortized Deferred Financing Costs	$ 473,376		$ 473,376		472,875
5.0% Senior Notes due 2024 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage	5.00%		5.00%
Principal Amount	$ 500,000		$ 500,000		500,000
Unamortized Deferred Financing Costs	(4,227)		(4,227)		(4,688)
Principal Amount, Net of Unamortized Deferred Financing Costs	$ 495,773		$ 495,773		495,312
5.625% Senior Notes due 2025 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage	5.625%		5.625%
Principal Amount	$ 500,000		$ 500,000		500,000
Unamortized Deferred Financing Costs	(5,356)		(5,356)		(5,808)
Principal Amount, Net of Unamortized Deferred Financing Costs	$ 494,644		$ 494,644		494,192
6.75% Senior Notes due 2026 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage	6.75%		6.75%
Principal Amount	$ 500,000		$ 500,000		500,000
Unamortized Deferred Financing Costs	(5,989)		(5,989)		(6,407)
Principal Amount, Net of Unamortized Deferred Financing Costs	$ 494,011		$ 494,011		493,593
6.625% Senior Notes due 2027 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage	6.625%		6.625%
Principal Amount	$ 500,000		$ 500,000		500,000
Unamortized Deferred Financing Costs	(7,067)		(7,067)		(7,533)
Principal Amount, Net of Unamortized Deferred Financing Costs	492,933		492,933		492,467
Senior Notes
Senior Notes [Line Items]
Principal Amount	2,476,796		2,476,796		2,476,796
Unamortized Deferred Financing Costs	(26,059)		(26,059)		(28,357)
Principal Amount, Net of Unamortized Deferred Financing Costs	$ 2,450,737		$ 2,450,737		$ 2,448,439