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Common Stock And Changes In Capitalization (Details) - USD ($) $ in Thousands |  |  | 6 Months Ended
--- | --- | --- | ---
Jun. 12, 2015 | Apr. 21, 2015 | Jun. 30, 2015 | Jun. 30, 2014
Class of Stock [Line Items] |  |  |  |
Proceeds from issuance of common stock, net of offering costs and exercise of stock options | $ 479,800 | $ 501,900 | $ 981,866 | $ 648
Common Stock [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock issued in underwritten public offering (in shares) | 11,500,000 | 10,925,000 | 22,425,000 |
Common Stock [Member] | Underwritten Public Offering [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock issued in underwritten public offering (in shares) | 1,500,000 | 1,425,000 |  |

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