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Long-Term Debt (Details) - USD ($) |  |  |  |  |  | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May. 21, 2015 | Nov. 17, 2014 | May. 20, 2013 | Jun. 29, 2012 | Nov. 08, 2011 | Jun. 30, 2015 | Jun. 30, 2015 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Jun. 22, 2015 | Jun. 05, 2015 | May. 20, 2015
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | $ 2,350,000,000 | $ 2,200,000,000 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 34,030,000 | 33,555,000 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | 2,315,970,000 | 2,166,445,000 | [1] |  |  |  |
Gains (Losses) on Extinguishment of Debt |  |  |  |  |  |  |  | (16,578,000) | 0 |  | $ 0 |  |  |
Gains (Losses) on Extinguishment of Debt, Non-Cash Portion |  |  |  |  |  |  |  | 4,123,000 | 0 |  | 0 |  |  |
Net proceeds from debt issuance |  |  |  |  |  |  |  | 490,951,000 | 589,991,000 |  | 490,185,000 |  |  |
Interest Costs, Capitalized During Period |  |  |  |  |  |  |  | 25,100,000 | 16,200,000 |  | $ 11,000,000 |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Covenant Compliance, Dividends Excluded From Computation |  |  |  |  |  |  |  | 6,500,000 |  |  |  |  |  |
6.625% Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | 0 | 350,000,000 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 0 | 4,591,000 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | $ 0 | 345,409,000 | [1] |  |  |  |
6.625% Senior Notes Due 2019 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  |  | 6.625% |  |  |  |  |  |
Price per Note Tendered |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,006.88 | $ 1,036.88
Debt Instrument, Face Amount, Individual Note |  |  |  |  |  |  |  |  |  |  |  |  | 1,000 | 1,000
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  |  |  | 1,500,000 | $ 242,900,000
Percentage of Notes Tendered |  |  |  |  |  |  |  |  |  |  |  |  |  | 69.00%
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,600,000 | $ 256,200,000
Gains (Losses) on Extinguishment of Debt |  |  |  |  |  | $ (16,578,000) |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Premium |  |  |  |  |  | 12,500,000 |  |  |  |  |  |  |  |
Gains (Losses) on Extinguishment of Debt, Non-Cash Portion |  |  |  |  |  | $ 4,123,000 |  |  |  |  |  |  |  |
6.625% Senior Notes Due 2019 [Member] | From February 15, 2015 to February 14, 2016 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  | $ 111,500,000 |  |
Debt Instrument, Redemption Price, Percentage |  |  |  |  |  |  | 103.313% |  |  |  |  |  |  |
6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | $ 350,000,000 | 350,000,000 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 4,106,000 | 4,806,000 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | 345,894,000 | 345,194,000 | [1] |  |  |  |
6.50% Senior Notes Due 2021 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 350,000,000 |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 6.50% |  |  |  |  |  |  |  |  |
Net proceeds from debt issuance |  |  |  |  | $ 343,100,000 |  |  |  |  |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  |  | $ 6,900,000 |  |  |  |  |  |  |  |  |
6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | 600,000,000 | 600,000,000 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 8,714,000 | 9,812,000 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | 591,286,000 | 590,188,000 | [1] |  |  |  |
6.125% Senior Notes Due 2022 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  | $ 600,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  | 6.125% |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from debt issuance |  | $ 590,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Deferred Finance Costs, Gross |  | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |
6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | 400,000,000 | 400,000,000 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 5,231,000 | 5,969,000 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | 394,769,000 | 394,031,000 | [1] |  |  |  |
6.50% Senior Notes Due 2023 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 400,000,000 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  | 6.50% |  |  |  |  |  |  |  |  |  |
Net proceeds from debt issuance |  |  |  | $ 392,100,000 |  |  |  |  |  |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  | $ 7,900,000 |  |  |  |  |  |  |  |  |  |
5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | 500,000,000 | 500,000,000 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 7,455,000 | 8,377,000 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | 492,545,000 | 491,623,000 | [1] |  |  |  |
5% Senior Notes Due 2024 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  | $ 500,000,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  | 5.00% |  |  |  |  |  |  |  |  |  |  |
Net proceeds from debt issuance |  |  | $ 490,200,000 |  |  |  |  |  |  |  |  |  |  |
Deferred Finance Costs, Gross |  |  | $ 9,800,000 |  |  |  |  |  |  |  |  |  |  |
5.625% Senior Notes Due 2025 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | 500,000,000 | 0 | [1] |  |  |  |
Unamortized Debt Issuance Expense |  |  |  |  |  |  |  | 8,524,000 | 0 | [1] |  |  |  |
Senior Notes, net of unamortized deferred financing costs (note 5) |  |  |  |  |  |  |  | $ 491,476,000 | $ 0 | [1] |  |  |  |
5.625% Senior Notes Due 2025 [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount | $ 500,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 5.625% |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds from debt issuance | $ 491,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred Finance Costs, Gross | $ 9,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | Prior period amounts have been reclassified to conform to the current period presentation on the accompanying balance sheets. Please refer to the section Recently Issued Accounting Standards in Note 1 – Summary of Significant Accounting Policies for additional discussion.

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