Common Stock	12 Months Ended
Dec. 31, 2013
Equity [Abstract]
Common Stock	7. Common Stock In June 2011, we completed a follow-on offering of common stock in which we sold a total of 6,095,000 shares of our common stock and received cash proceeds of $172.7 million from this transaction, net of underwriting discounts. Concurrent with this offering, we also sold 1,416,000 shares of our common stock to our CEO and 637,475 shares of our common stock to Blackstar Investco LLC, an affiliate of Daimler and received total cash proceeds of $59.1 million in the private placements. No underwriting discounts or commissions were paid in connection with these private placements. In October 2012, we completed a follow-on offering of common stock in which we sold a total of 7,964,601 shares of our common stock and received cash proceeds of $222.1 million (which included 35,398 shares or $1.0 million sold to our CEO) from this transaction, net of underwriting discounts and offering costs. In May 2013, we completed a public offering of common stock and sold a total of 3,902,862 shares of our common stock for total cash proceeds of approximately $355.5 million (which included 487,857 shares or $45.0 million sold to our CEO), net of underwriting discounts and offering costs. We also sold 596,272 shares of our common stock to our CEO and received total cash proceeds of $55.0 million in a private placement at the public offering price. Concurrent with these equity transactions, we also issued $660.0 million principal amount of 1.50% convertible senior notes in a public offering and received total cash proceeds of approximately $648.0 million, net of underwriting discounts and offering costs (see Note 6).

Common Stock

12 Months Ended

Dec. 31, 2013

7. Common Stock

In June 2011, we completed a follow-on offering of common stock in which we sold a total of 6,095,000 shares of our common stock and received cash proceeds of $172.7 million from this transaction, net of underwriting discounts. Concurrent with this offering, we also sold 1,416,000 shares of our common stock to our CEO and 637,475 shares of our common stock to Blackstar Investco LLC, an affiliate of Daimler and received total cash proceeds of $59.1 million in the private placements. No underwriting discounts or commissions were paid in connection with these private placements.

In October 2012, we completed a follow-on offering of common stock in which we sold a total of 7,964,601 shares of our common stock and received cash proceeds of $222.1 million (which included 35,398 shares or $1.0 million sold to our CEO) from this transaction, net of underwriting discounts and offering costs.

In May 2013, we completed a public offering of common stock and sold a total of 3,902,862 shares of our common stock for total cash proceeds of approximately $355.5 million (which included 487,857 shares or $45.0 million sold to our CEO), net of underwriting discounts and offering costs. We also sold 596,272 shares of our common stock to our CEO and received total cash proceeds of $55.0 million in a private placement at the public offering price. Concurrent with these equity transactions, we also issued $660.0 million principal amount of 1.50% convertible senior notes in a public offering and received total cash proceeds of approximately $648.0 million, net of underwriting discounts and offering costs (see Note 6).