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Senior Notes(Details) - USD ($) |  |  |  |  |  | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May 21, 2015 | Nov. 17, 2014 | May 20, 2013 | Jun. 29, 2012 | Nov. 08, 2011 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Mar. 31, 2017 | Sep. 12, 2016
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | $ 2,769,663,000 | $ 2,766,719,000 |  |  |
Gain (loss) on extinguishment of debt |  |  |  |  |  |  | (35,000) | 15,722,000 | $ (16,578,000) |  |
Loss on extinguishment of debt, acceleration of unamortized deferred financing costs |  |  |  |  |  |  | $ 22,000 | (15,722,000) | 4,123,000 |  |
6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.50% |  |  |  |
Senior Notes, face amount |  |  |  |  | $ 350,000,000 |  |  | 346,955,000 |  |  |
Unamortized deferred financing costs |  |  |  |  |  |  | $ 2,656,000 | 3,372,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | $ 341,955,000 | 343,583,000 |  |  |
Senior Notes, repurchased face amount |  |  |  |  |  | $ 3,100,000 |  |  |  | $ 2,300,000 |
Senior Notes, repurchased settlement amount |  |  |  |  |  | 2,300,000 |  |  |  |  |
Net proceeds from Senior Notes issuance |  |  |  |  | 343,100,000 |  |  |  |  |  |
Senior Notes debt issuance costs, gross |  |  |  |  | $ (6,900,000) |  |  |  |  |  |
6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.125% |  |  |  |
Senior Notes, face amount |  | $ 600,000,000 |  |  |  |  |  | 561,796,000 |  |  |
Unamortized deferred financing costs |  |  |  |  |  |  | $ 5,800,000 | 6,979,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | $ 555,996,000 | 554,817,000 |  |  |
Senior Notes, repurchased face amount |  |  |  |  |  | 38,200,000 |  |  |  |  |
Senior Notes, repurchased settlement amount |  |  |  |  |  | 24,300,000 |  |  |  |  |
Net proceeds from Senior Notes issuance |  | 590,000,000 |  |  |  |  |  |  |  |  |
Senior Notes debt issuance costs, gross |  | $ (10,000,000) |  |  |  |  |  |  |  |  |
6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.50% |  |  |  |
Senior Notes, face amount |  |  |  | $ 400,000,000 |  |  |  | 394,985,000 |  |  |
Unamortized deferred financing costs |  |  |  |  |  |  | $ 3,707,000 | 4,436,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | $ 391,278,000 | 390,549,000 |  |  |
Senior Notes, repurchased face amount |  |  |  |  |  | 5,000,000 |  |  |  |  |
Senior Notes, repurchased settlement amount |  |  |  |  |  | 3,300,000 |  |  |  |  |
Net proceeds from Senior Notes issuance |  |  |  | 392,100,000 |  |  |  |  |  |  |
Senior Notes debt issuance costs, gross |  |  |  | $ (7,900,000) |  |  |  |  |  |  |
5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 5.00% |  |  |  |
Senior Notes, face amount |  |  | $ 500,000,000 |  |  |  |  | 500,000,000 |  |  |
Unamortized deferred financing costs |  |  |  |  |  |  | $ 5,610,000 | 6,533,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | $ 494,390,000 | 493,467,000 |  |  |
Net proceeds from Senior Notes issuance |  |  | 490,200,000 |  |  |  |  |  |  |  |
Senior Notes debt issuance costs, gross |  |  | $ (9,800,000) |  |  |  |  |  |  |  |
5.625% Senior Notes Due 2025 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 5.625% |  |  |  |
Senior Notes, face amount | $ 500,000,000 |  |  |  |  |  |  | 500,000,000 |  |  |
Unamortized deferred financing costs |  |  |  |  |  |  | $ 6,714,000 | 7,619,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | $ 493,286,000 | 492,381,000 |  |  |
Net proceeds from Senior Notes issuance | 491,000,000 |  |  |  |  |  |  |  |  |  |
Senior Notes debt issuance costs, gross | $ (9,000,000) |  |  |  |  |  |  |  |  |  |
6.75% Senior Notes Due 2026 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.75% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  |  | 500,000,000 |  |  | $ 500,000,000
Unamortized deferred financing costs |  |  |  |  |  |  | $ 7,242,000 | 8,078,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | 492,758,000 | 491,922,000 |  |  |
Net proceeds from Senior Notes issuance |  |  |  |  |  |  |  | 491,600,000 |  |  |
Senior Notes debt issuance costs, gross |  |  |  |  |  |  |  |  |  |  | $ (8,400,000)
6.625% Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on extinguishment of debt |  |  |  |  |  |  |  |  | (16,600,000) |  |
Loss on extinguishment of debt, acceleration of unamortized deferred financing costs |  |  |  |  |  |  |  |  | (4,100,000) |  |
Senior Notes, repurchase premium |  |  |  |  |  |  |  |  | $ 12,500,000 |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | 2,801,392,000 | 2,803,736,000 |  |  |
Unamortized deferred financing costs |  |  |  |  |  |  | 31,729,000 | 37,017,000 |  |  |
Senior Notes, net of unamortized deferred financing costs |  |  |  |  |  |  | 2,769,663,000 | 2,766,719,000 |  |  |
Senior Notes, covenant compliance, dividends excluded from computation |  |  |  |  |  |  | $ 6,500,000 |  |  |  |
Senior Notes, repurchased face amount |  |  |  |  |  | 46,300,000 |  |  |  |  |
Senior Notes, repurchased settlement amount |  |  |  |  |  | $ 29,900,000 |  |  |  |  |
Gain (loss) on extinguishment of debt |  |  |  |  |  |  |  | 15,700,000 |  |  |
Senior Notes, repurchase discount |  |  |  |  |  |  |  | 16,400,000 |  |  |
Loss on extinguishment of debt, acceleration of unamortized deferred financing costs |  |  |  |  |  |  |  | (700,000) |  |  |
Senior Notes [Member] | 6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.50% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | $ 344,611,000 | 346,955,000 |  |  |
Senior Notes [Member] | 6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.125% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | $ 561,796,000 | 561,796,000 |  |  |
Senior Notes [Member] | 6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.50% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | $ 394,985,000 | 394,985,000 |  |  |
Senior Notes [Member] | 5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 5.00% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | $ 500,000,000 | 500,000,000 |  |  |
Senior Notes [Member] | 5.625% Senior Notes Due 2025 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 5.625% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | $ 500,000,000 | 500,000,000 |  |  |
Senior Notes [Member] | 6.75% Senior Notes Due 2026 [Member] |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior Notes, interest rate, stated percentage |  |  |  |  |  |  | 6.75% |  |  |  |
Senior Notes, face amount |  |  |  |  |  |  | $ 500,000,000 | $ 500,000,000 |  |  |

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