Stockholder Rights Plan	6 Months Ended
Jun. 30, 2013
Equity [Abstract]
Stockholder Rights Plan	Stockholder Rights Plan and Protective Amendment We have a stockholder rights plan, or the Rights Plan, established under the terms of a rights agreement dated December 21, 2006, as amended, with Computershare Trust Company N.A., as Rights Agent, or the Rights Agreement. Our board of directors adopted the Rights Plan to protect our stockholders from coercive takeover practices or takeover bids that are inconsistent with their best interests. On March 22, 2013, our board of directors approved an amendment to the Rights Agreement in an effort to protect our net operating loss carryforwards during the effective period of the amendment. Under this amendment, if any person becomes the beneficial owner of 4.9% or more of our common stock, stockholders other than the 4.9% triggering stockholder will have the right to purchase additional shares of our common stock at half the market price, thereby diluting the triggering stockholder; provided that stockholders whose beneficial ownership exceeded 4.9% of our common stock outstanding on March 22, 2013 will not be deemed to have triggered the Rights Agreement, as amended, so long as they do not thereafter acquire additional common stock other than in certain specified exempt transactions. In addition, a person generally will not be deemed to have triggered the Rights Agreement, as amended, by virtue of the conversion of our convertible notes. The amendment to the Rights Agreement is effective until the earlier of (i) March 22, 2016, (ii) the date on which our board of directors determines that the amendment is no longer necessary for the provision of certain tax benefits because of the repeal of Section 382 of the Internal Revenue Code, or Code, (iii) the first day of a taxable year as to which our board of directors determines that no tax benefits may be carried forward, or (iv) such other date as our board of directors determines that the amendment is no longer necessary for the preservation of tax benefits. Upon expiration of the amendment to the Rights Agreement, the triggering threshold level under the Rights Plan will revert to the 15% level in effect prior to the amendment, unless our board of directors determines otherwise. Our stockholders ratified, on an advisory basis, the amendment to the Rights Agreement at our 2013 annual meeting of stockholders. Prior to the adoption of the amendments to the Rights Agreement described above, under the Rights Plan, if any person or group were to acquire beneficial ownership of 15% or more of our then-outstanding voting stock, stockholders other than the 15% triggering stockholder would have had the right to purchase additional shares of our common stock at half the market price, thereby diluting the triggering stockholder. The Rights Agreement also provides that, during the standstill period under the terms of a shareholder's agreement we entered into with Berkshire Hathaway, Inc., an acquisition of shares of our common stock by Berkshire Hathaway (or certain of its affiliates) will not trigger the rights to the extent Berkshire Hathaway complies with the terms of the shareholder's agreement and, following the expiration of the standstill period, Berkshire Hathaway (and certain of its affiliates) will not trigger the rights unless Berkshire Hathaway and its affiliates acquire beneficial ownership of more than 50% of our voting stock on a fully diluted basis. The rights issued pursuant to the Rights Agreement will expire on January 2, 2017. However, our board of directors has the power to accelerate or extend the expiration date of the rights. In addition, a board committee composed solely of independent directors will review the Rights Agreement at least once every three years to determine whether to modify the Rights Plan in light of all relevant factors. This review was most recently conducted in November 2012. The next review is required by the end of 2015. On May 9, 2013, we filed an amendment to our Restated Certificate of Incorporation, or the Protective Amendment, that restricts certain transfers of our common stock. The Protective Amendment is intended to protect the tax benefits of our net operating loss, or NOL, carryforwards. See Note 17 for a description of our NOL carryforwards. Subject to certain limited exceptions, the Protective Amendment's transfer restrictions would restrict any person from transferring our common stock (or any interest in our common stock) if the transfer would result in a stockholder (or several stockholders, in the aggregate, who hold their stock as a “group” under Section 382 of the Code) owning 4.9% or more of our common stock. Any direct or indirect transfer attempted in violation of the Protective Amendment would be void as of the date of the prohibited transfer as to the purported transferee, and the purported transferee would not be recognized as the owner of the shares attempted to be owned in violation of the Protective Amendment for any purpose, including for purposes of voting and receiving dividends or other distributions in respect of that common stock, or in the case of options, receiving our common stock in respect of their exercise. The Protective Amendment is effective until the earlier of (i) May 9, 2016, (ii) the repeal of Section 382 of the Code if our board of directors determines that the Protective Amendment is no longer necessary for the preservation of tax benefits, (iii) the first day of a taxable year as to which our board of directors determines that no tax benefits may be carried forward, or (iv) such other date as determined by our board of directors pursuant to the Protective Amendment.

Stockholder Rights Plan and Protective Amendment

We have a stockholder rights plan, or the Rights Plan, established under the terms of a rights agreement dated December 21, 2006, as amended, with Computershare Trust Company N.A., as Rights Agent, or the Rights Agreement. Our board of directors adopted the Rights Plan to protect our stockholders from coercive takeover practices or takeover bids that are inconsistent with their best interests.

On March 22, 2013, our board of directors approved an amendment to the Rights Agreement in an effort to protect our net operating loss carryforwards during the effective period of the amendment. Under this amendment, if any person becomes the beneficial owner of 4.9% or more of our common stock, stockholders other than the 4.9% triggering stockholder will have the right to purchase additional shares of our common stock at half the market price, thereby diluting the triggering stockholder; provided that stockholders whose beneficial ownership exceeded 4.9% of our common stock outstanding on March 22, 2013 will not be deemed to have triggered the Rights Agreement, as amended, so long as they do not thereafter acquire additional common stock other than in certain specified exempt transactions. In addition, a person generally will not be deemed to have triggered the Rights Agreement, as amended, by virtue of the conversion of our convertible notes.

The amendment to the Rights Agreement is effective until the earlier of (i) March 22, 2016, (ii) the date on which our board of directors determines that the amendment is no longer necessary for the provision of certain tax benefits because of the repeal of Section 382 of the Internal Revenue Code, or Code, (iii) the first day of a taxable year as to which our board of directors determines that no tax benefits may be carried forward, or (iv) such other date as our board of directors determines that the amendment is no longer necessary for the preservation of tax benefits. Upon expiration of the amendment to the Rights Agreement, the triggering threshold level under the Rights Plan will revert to the 15% level in effect prior to the amendment, unless our board of directors determines otherwise. Our stockholders ratified, on an advisory basis, the amendment to the Rights Agreement at our 2013 annual meeting of stockholders.

Prior to the adoption of the amendments to the Rights Agreement described above, under the Rights Plan, if any person or group were to acquire beneficial ownership of 15% or more of our then-outstanding voting stock, stockholders other than the 15% triggering stockholder would have had the right to purchase additional shares of our common stock at half the market price, thereby diluting the triggering stockholder. The Rights Agreement also provides that, during the standstill period under the terms of a shareholder's agreement we entered into with Berkshire Hathaway, Inc., an acquisition of shares of our common stock by Berkshire Hathaway (or certain of its affiliates) will not trigger the rights to the extent Berkshire Hathaway complies with the terms of the shareholder's agreement and, following the expiration of the standstill period, Berkshire Hathaway (and certain of its affiliates) will not trigger the rights unless Berkshire Hathaway and its affiliates acquire beneficial ownership of more than 50% of our voting stock on a fully diluted basis.

The rights issued pursuant to the Rights Agreement will expire on January 2, 2017. However, our board of directors has the power to accelerate or extend the expiration date of the rights. In addition, a board committee composed solely of independent directors will review the Rights Agreement at least once every three years to determine whether to modify the Rights Plan in light of all relevant factors. This review was most recently conducted in November 2012. The next review is required by the end of 2015.

On May 9, 2013, we filed an amendment to our Restated Certificate of Incorporation, or the Protective Amendment, that restricts certain transfers of our common stock. The Protective Amendment is intended to protect the tax benefits of our net operating loss, or NOL, carryforwards. See Note 17 for a description of our NOL carryforwards. Subject to certain limited exceptions, the Protective Amendment's transfer restrictions would restrict any person from transferring our common stock (or any interest in our common stock) if the transfer would result in a stockholder (or several stockholders, in the aggregate, who hold their stock as a “group” under Section 382 of the Code) owning 4.9% or more of our common stock. Any direct or indirect transfer attempted in violation of the Protective Amendment would be void as of the date of the prohibited transfer as to the purported transferee, and the purported transferee would not be recognized as the owner of the shares attempted to be owned in violation of the Protective Amendment for any purpose, including for purposes of voting and receiving dividends or other distributions in respect of that common stock, or in the case of options, receiving our common stock in respect of their exercise. The Protective Amendment is effective until the earlier of (i) May 9, 2016, (ii) the repeal of Section 382 of the Code if our board of directors determines that the Protective Amendment is no longer necessary for the preservation of tax benefits, (iii) the first day of a taxable year as to which our board of directors determines that no tax benefits may be carried forward, or (iv) such other date as determined by our board of directors pursuant to the Protective Amendment.