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Equity Investments (Narrative) (Details) a in Thousands, $ in Thousands |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Nov. 12, 2014 USD ($) shares | Jan. 28, 2014 USD ($) | Mar. 31, 2015 USD ($) | Sep. 30, 2014 USD ($) shares | Jun. 30, 2014 shares | Sep. 30, 2015 USD ($) | Mar. 31, 2015 USD ($) | Sep. 30, 2014 USD ($) | Mar. 31, 2014 USD ($) | Sep. 30, 2015 USD ($) a shares | Sep. 30, 2014 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) shares | Dec. 31, 2012 | Oct. 11, 2012 USD ($) shares
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distributions received |  |  |  |  |  |  |  |  |  | $ 4,761 | $ 476 |  |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 295,103 |  |  |  | 295,103 |  | $ 369,581 |  |  |
(Income) loss from equity method investments |  |  |  |  |  | $ 61,891 |  | $ 34,477 |  | 57,036 | (163,567) |  |  |  |
Payments for equity method investments |  |  |  |  |  |  |  |  |  | $ 13,837 | 61,750 |  |  |  |
Apico Llc [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity shares owned by affiliate (shares) | shares |  |  |  |  |  |  |  |  |  | 85,122 |  |  |  |  |
Total shares owned of subaffiliate (shares) | shares |  |  |  |  |  |  |  |  |  | 1,000,000 |  |  |  |  |
Gas and oil area, reserve (acres) | a |  |  |  |  |  |  |  |  |  | 243 |  |  |  |  |
Tatex Thailand III, LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas and oil area, reserve (acres) | a |  |  |  |  |  |  |  |  |  | 245 |  |  |  |  |
Ownership interest |  |  |  |  |  | 17.90% |  |  |  | 17.90% |  |  |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  |  |
(Income) loss from equity method investments |  |  |  |  |  | 0 |  | 47 |  | $ 0 | 217 |  |  |  |
Grizzly Oil Sands ULC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gas and oil area, reserve (acres) | a |  |  |  |  |  |  |  |  |  | 830 |  |  |  |  |
Unrealized gain investments |  |  |  |  |  |  |  |  |  | $ 58,000 |  |  |  |  |
Cash calls paid |  |  |  |  |  |  |  |  |  | 13,800 |  |  |  |  |
Increase (decrease) due to foreign currency translation adjustment |  |  |  |  |  | $ (11,600) |  | (9,500) |  | $ (23,300) | (10,000) |  |  |  |
Ownership interest |  |  |  |  |  | 24.9999% |  |  |  | 24.9999% |  |  |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  |  |  |  |  |  |  | 180,218 |  |  |
(Income) loss from equity method investments |  |  |  |  |  | $ 58,653 |  | 4,633 |  | $ 71,289 | 8,862 |  |  |  |
Windsor Midstream LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  | 22.50% |  |  |  | 22.50% |  |  |  |  |
Distributions received |  |  |  |  |  |  |  |  |  | $ 3,800 |  |  |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 27,940 |  |  |  | 27,940 |  | 13,505 |  |  |
(Income) loss from equity method investments |  |  |  |  |  | $ (323) |  | (301) |  | $ (18,229) | (504) |  |  |  |
Windsor Midstream LLC [Member] | MidMar Gas LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  | 28.40% |
Coronado Midstream [Member] | Windsor Midstream LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from sale of interest in partnership unit |  |  | $ 600,000 |  |  |  |  |  |  |  |  |  |  |  |
Gain on sale on investment |  |  | $ 81,600 |  |  |  |  |  |  |  |  |  |  |  |
Blackhawk Midstream LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  | 48.50% |  |  |  | 48.50% |  |  |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 0 |  |  |  | $ 0 |  | 0 |  |  |
(Income) loss from equity method investments |  |  |  |  |  | $ 0 |  | 0 |  | $ (7,217) | (84,787) |  |  |  |
Blackhawk Midstream LLC [Member] | Ohio Gathering Company, LLC and Ohio Condensate Company, LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price of sold equity interests |  | $ 190,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Amount put in escrow |  | $ 14,300 |  |  |  |  |  |  |  |  |  |  |  |  |
Distributions received |  |  |  |  |  |  |  |  | $ 84,800 |  |  |  |  |  |
Proceeds from release of escrow deposits |  |  |  |  |  |  | $ 7,200 |  |  |  |  |  |  |  |
Diamondback Energy, Inc [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  | 0.00% |  |  |  | 0.00% |  |  |  |  |
Investment (shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7,914,036
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 0 |  |  |  | $ 0 |  | $ 0 |  |  | $ 138,500
Number of shares issued in transaction (shares) | shares | 942,000 |  |  | 1,437,500 | 1,000,000 |  |  |  |  |  |  |  | 4,534,536 |  |
Proceeds received from sale of stock | $ 60,800 |  |  | $ 197,600 |  |  |  |  |  |  |  |  | $ 192,700 |  |
(Income) loss from equity method investments |  |  |  |  |  | $ 0 |  | 32,412 |  | $ 0 | (89,300) |  |  |  |
Sturgeon Acquisitions LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  | 25.00% |  |  |  | 25.00% |  | 25.00% |  |  |
Distributions received |  |  |  |  |  |  |  |  |  | $ 1,000 |  |  |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 22,857 |  |  |  | 22,857 |  | $ 22,507 |  |  |
(Income) loss from equity method investments |  |  |  |  |  | $ (257) |  | 0 |  | $ (1,316) | 0 |  |  |  |
Payments for equity method investments |  |  |  |  |  |  |  |  |  |  |  | $ 20,700 |  |  |
Mammoth Energy Partners LP [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  | 30.50% |  |  |  | 30.50% |  | 30.50% |  |  |
Equity investments and investments in subsidiaries |  |  |  |  |  | $ 135,971 |  |  |  | $ 135,971 |  | $ 143,973 |  |  |
(Income) loss from equity method investments |  |  |  |  |  | $ 3,612 |  | $ 0 |  | $ 11,608 | $ 0 |  |  |  |
Equity investment in Mammoth Energy Partners |  |  |  |  |  |  |  |  |  |  |  | $ 143,500 |  |  |

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