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Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions |  | 1 Months Ended |
--- | --- | --- | ---
Jul. 23, 2015 | Apr. 30, 2017 | Jun. 30, 2017
Class of Warrant or Right [Line Items] |  |  |
Common stock, beneficial ownership threshold to be considered an Acquiring Person (as a percent) | 5.00% |  |
Common shares purchasable per Right (in shares) | 0.1 |  |
Shareholder rights accompanying each outstanding share of the company's common stock (in number of Rights) | 1 |  |
Purchase price (in dollars per share) | $ 45 |  |
Purchase price (in dollars per share) | 4.50 |  |
Redemption price (in dollars per Right) | $ 0.001 |  |
Rights |  |  |
Class of Warrant or Right [Line Items] |  |  |
Number of rights per outstanding share of common stock (in shares) | 1 |  |
Period after public announcement that a person has become an acquirer (in days) | 10 days |  |
Period after a person announces a tender offer which would make them an acquirer (in days) | 10 days |  |
2% Notes |  |  |
Class of Warrant or Right [Line Items] |  |  |
Stated interest rate (in hundredths) |  |  | 2.00%
Principal amount of notes converted into shares |  | $ 202.5 |
Convertible Senior Notes |  |  |
Class of Warrant or Right [Line Items] |  |  |
Stated interest rate (in hundredths) |  |  | 5.00%
Convertible Senior Notes | 2% Convertible Senior Notes |  |  |
Class of Warrant or Right [Line Items] |  |  |
Shares issued during period upon conversion of convertible debt (in shares) |  | 29,100,000 |
Treasury stock reissued during period upon conversion of notes (in shares) |  | 18,700,000 |
Stock issued during period upon conversion of notes (in shares) |  | 10,400,000 |

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