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Debt (Narrative) (Details) | 3 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2017 | Mar. 31, 2017 USD ($) | Dec. 31, 2013 | Dec. 31, 2012 USD ($) | Dec. 31, 2019 USD ($) $ / shares | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2015 USD ($) | Sep. 30, 2019 USD ($) | Mar. 31, 2018 USD ($) | Feb. 28, 2018 USD ($) | Feb. 09, 2018 USD ($) | Oct. 31, 2017 USD ($) | Jun. 30, 2017 USD ($) | Jan. 05, 2017 USD ($) | Dec. 31, 2016 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tender Offer |  |  |  |  |  | $ 985,000,000.0 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | $ 951,800,000 | 721,800,000 | $ 194,100,000 |  |  | $ 595,400,000 |  |  |  |  |  |
Extinguishment of Debt, Gain (Loss), Net of Tax |  |  |  |  |  | 19,000,000.0 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  | 724,100,000 | 771,200,000 | 204,500,000 |  |  |  |  |  |  |  |  |
Gain (Loss) on Extinguishment of Debt |  | $ 6,200,000 |  |  | 194,100,000 | (19,000,000.0) | (2,600,000) |  |  |  |  |  |  |  |  |
Interest Expense |  |  |  |  | 428,300,000 | 282,700,000 | 224,200,000 |  |  |  |  |  |  |  |  |
Capitalized interest |  |  |  |  | $ 20,900,000 | 62,600,000 | 72,500,000 |  |  |  |  |  |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Redemption Price, Percentage |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |  |  |
Debentures Due 2027 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Redemption Price, Percentage |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |  |  |
7.38%SeniorNotesDue2025 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.375% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2025 |  |  |  |  |  |  |  |  |  |  |
5.40%SeniorNotesDue2042 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 5.40% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2042 |  |  |  |  |  |  |  |  |  |  |
5.85%SeniorNotesDue2044 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 5.85% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2044 |  |  |  |  |  |  |  |  |  |  |
3.00% Exchangeable senior notes due 2024(2) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 3.00% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2024 |  |  |  |  |  |  |  |  |  |  |
7.875% Senior Notes Due 2040 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.875% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2040 |  |  |  |  |  |  |  |  |  |  |
4.875%SeniorNotesDue2022Member [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 4.875% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2022 |  |  |  |  |  |  |  |  |  |  |
4.75%SeniorNotesDue2024Member [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 4.75% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2024 |  |  |  |  |  |  |  |  |  |  |
7.75% Senior notes due 2026 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.75% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2026 |  |  |  |  |  |  |  |  |  |  |
5.20% Senior notes due 2025(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 5.20% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2025 |  |  |  |  |  |  |  |  |  |  |
5.75% Senior notes due 2044 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 5.75% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2044 |  |  |  |  |  |  |  |  |  |  |
4.50% Senior notes due 2024(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 4.50% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2024 |  |  |  |  |  |  |  |  |  |  |
4.70% Senior notes due 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 4.70% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2021 |  |  |  |  |  |  |  |  |  |  |
6.875% Senior notes due 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 6.875% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2020 |  |  |  |  |  |  |  |  |  |  |
8.50% Senior notes due 2019(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 8.50% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2019 |  |  |  |  |  |  |  |  |  |  |
7.875% Senior notes due 2040 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.875% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2040 |  |  |  |  |  |  |  |  |  |  |
7.20% Senior notes due 2027 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.20% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2027 |  |  |  |  |  |  |  |  |  |  |
8.00% Senior notes due 2024(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 8.00% |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2024 |  |  |  |  |  |  |  |  |  |  |
Open Market Repurchases [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  | 194,100,000 |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  | 204,500,000 |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] | Five Year Credit Facility Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current borrowing capacity |  |  |  |  |  | 1,600,000,000 |  |  |  |  |  |  | $ 2,000,000,000.0 |  |  |
Potential_Additional_Revolver_Capacity |  |  |  |  | $ 250,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  |  |  |  | 0.75% |  |  |  |  |  |  |  |  |  |  |
Maximum Percent of Debt to Total Capitalization Ratio |  |  |  |  | 60.00% |  |  |  |  |  |  |  |  |  |  |
Line of Credit Facility, Fair Value of Amount Outstanding |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |
Debt Covenant, Additional Secured Debt, Value |  |  |  |  | $ 1,000,000,000 |  |  |  |  |  |  |  |  |  |  |
Debt Covenant, Additional Secured Debt, Percent Of Tangible Net Worth |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |
Common Stock, Dividends, Per Share, Cash Paid | $ / shares |  |  |  |  | $ 0.01 |  |  |  |  |  |  |  |  |  |  |
Debt Covenant, Aggregate Amount Of Available Cash |  |  |  |  | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] | Credit Facility due 2020 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current borrowing capacity |  |  |  |  | 1,200,000,000 |  |  |  |  |  |  |  | $ 1,300,000,000 |  |  |
Revolving Credit Facility [Member] | Credit Facility due 2019 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current borrowing capacity |  |  |  |  | $ 1,600,000,000 |  |  |  |  |  |  |  |  |  |  |
Debt Covenant, Period For Repayment Of Acquired Companies |  |  |  |  | 90 days |  |  |  |  |  |  |  |  |  |  |
Debt Covenant, Aggregate Amount Of Available Cash, After Repayments |  |  |  |  | $ 250,000,000 |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] | Base Rate [Member] | Five Year Credit Facility Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  |  | 3.25% |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Five Year Credit Facility Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  |  | 4.25% |  |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | 3.00% Exchangeable senior notes due 2024(2) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 8.00% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 849,500,000 | 849,500,000 |  |  |  |  |  |  |  |  |  | $ 849,500,000
Senior Note Maturity Year |  |  |  |  | 2024 |  |  |  |  |  |  |  |  |  |  |
Conversion rate per $1,000 principal amount of shares |  |  |  |  | 17.8336 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Convertible, Conversion Price | $ / shares |  |  |  |  | $ 56.08 |  |  |  |  |  |  |  |  |  |  |
Interest Expense, Debt, Excluding Amortization |  |  |  |  | $ 25,500,000 |  |  |  |  |  |  |  |  |  |  |
Amortization of Debt Issuance Costs and Discounts |  |  |  |  | $ 32,500,000 | 31,000,000.0 | 31,400,000 |  |  |  |  |  |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  | 311,200,000 |  |  |  |  |  |  |  |  | 1,093,100,000
Senior Notes [Member] | 7.38%SeniorNotesDue2025 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.375% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 500,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | 139,200,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  | $ 109,200,000 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 5.40%SeniorNotesDue2042 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 5.40% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 400,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 5.85%SeniorNotesDue2044 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 5.85% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 400,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 7.875% Senior Notes Due 2040 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 7.875% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 201,400,000 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 4.875%SeniorNotesDue2022Member [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 4.875% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 620,800,000 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 4.75%SeniorNotesDue2024Member [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  | 4.75% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 398,100,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | 79,500,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  | $ 61,200,000 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 7.75% Senior notes due 2026 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  |  |  |  |  |  |  | 7.75% |  |  |  |  |  |
Debt Issuance Costs, Gross |  |  |  |  |  |  |  |  |  | $ (16,500,000) |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | 1,000,000,000.0 |  |  | $ 1,000,000,000.0 |  |  |  |  |  |  |
Senior Notes [Member] | 5.20% Senior notes due 2025(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 5.20% | 5.20% |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 700,000,000.0
Senior Note Maturity Year |  |  |  |  | 2025 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount (Premium), Net |  | $ 2,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | $ 335,500,000 |  |  |  |  |  |  |  |  |  |  | 30,700,000
Debt Instrument, Repurchase Amount |  |  |  |  | 250,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 5.75% Senior notes due 2044 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  | 5.75% |  |  |  |  |  | 5.75% |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  | $ 400,000,000.0 |  |  |  |  |  | $ 625,000,000.0 |  |  |  |  |  |  |  |
Senior Note Maturity Year | 2044 |  |  |  |  |  |  | 2044 |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount (Premium), Net |  | $ 18,700,000 |  |  |  |  |  | $ 2,800,000 |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 24,500,000
Senior Notes [Member] | 4.50% Senior notes due 2024(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 4.50% |  |  |  | 4.50% |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | $ 625,000,000.0 |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  |  |  |  | 2024 |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount (Premium), Net |  |  |  |  |  |  |  | $ 900,000 |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | 320,000,000.0 |  |  |  |  |  |  |  |  |  |  | 1,700,000
Debt Instrument, Repurchase Amount |  |  |  |  | $ 240,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 4.70% Senior notes due 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 4.70% |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 1,500,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  | 2021 | 2021 |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount (Premium), Net |  |  |  | $ 29,600,000 |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  | $ 156,200,000 | 413,300,000 |  |  | 156,200,000 |  |  |  | $ 39,400,000 |  | 817,000,000.0
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  | 159,700,000 |  |  |  | 39,300,000 |  |
Senior Notes [Member] | 6.875% Senior notes due 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 6.875% |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 900,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  | 2020 | 2020 |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  | $ 229,900,000 |  |  | 71,400,000 | $ 328,000,000.0 |  |  | 100,100,000 |  | 219,200,000
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  | $ 354,700,000 |  |  | 105,100,000 |  |
Senior Notes [Member] | 8.50% Senior notes due 2019(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 8.50% |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 500,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  | 2019 | 2019 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  | $ 55,000,000.0 |  | $ 237,600,000 |  | 54,600,000 |  |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  | $ 256,800,000 |  | $ 60,100,000 |  |
Senior Notes [Member] | 7.875% Senior notes due 2040 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 7.875% |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 300,000,000.0 |  |  |  |  |  |  |  |  |  |  |  | $ 300,000,000.0
Senior Note Maturity Year |  |  |  | 2040 |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 7.20% Senior notes due 2027 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 7.20% |  | 7.20% |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | $ 150,000,000.0 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | $ 37,900,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  | $ 29,900,000 |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | 8.00% Senior notes due 2024(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, interest rate, stated percentage |  |  |  | 8.00% | 8.00% | 8.00% |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | $ 332,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Senior Note Maturity Year |  |  |  |  | 2024 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  | $ 39,700,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchase Amount |  |  |  |  | $ 33,800,000 |  |  |  |  |  |  |  |  |  |  |
Exchange Offers [Member] | Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 649,500,000 |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 664,500,000 |
Exchange Offers [Member] | Senior Notes [Member] | 4.70% Senior notes due 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 373,900,000 |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 362,500,000 |
Exchange Offers [Member] | Senior Notes [Member] | 6.875% Senior notes due 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 129,800,000 |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 138,700,000 |
Exchange Offers [Member] | Senior Notes [Member] | 8.50% Senior notes due 2019(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 145,800,000 |
Debt Instrument, Repurchase Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 163,300,000 |
Exchange Offers [Member] | Senior Notes [Member] | 8.00% Senior notes due 2024(1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 332,000,000.0 |

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