Capital Stock	12 Months Ended
Dec. 31, 2011
Equity [Abstract]
Capital Stock	Capital Stock Common Shares We are authorized to issue up to 200,000,000 shares of common stock, $0.01 par value per share. Each outstanding share of common stock entitles the holder to one vote on all matters submitted to a vote of stockholders. Holders of our common stock are entitled to receive dividends out of assets legally available for the payment of dividends when authorized by our board of directors. Follow-On Public Offerings. On January 31, 2011, we completed a follow-on public offering of our common stock. We sold 12,418,662 shares of our common stock, including the underwriter’s option to purchase 1,418,662 additional shares, at a public offering price of $12.15 per share. The net proceeds to us, after deduction of offering costs, were approximately $149.6 million. On May 28, 2010, we completed a follow-on public offering of our common stock. We sold 23,000,000 shares of common stock, including the underwriters' overallotment of 3,000,000 shares, at a public offering price of $8.40 per share. The net proceeds to us, after deduction of offering costs, were approximately $184.6 million. Preferred Shares We are authorized to issue up to 10,000,000 shares of preferred stock, $0.01 par value per share. Our board of directors is required to set for each class or series of preferred stock the terms, preferences, conversion or other rights, voting powers, restrictions, limitations as to dividends or other distributions, qualifications, and terms or conditions of redemption. As of December 31, 2011 and 2010, there were no shares of preferred stock outstanding. Operating Partnership Units Holders of operating partnership units have certain redemption rights, which enable them to cause our operating partnership to redeem their units in exchange for cash per unit equal to the market price of our common stock, at the time of redemption, or, at our option for shares of our common stock on a one-for-one basis. The number of shares issuable upon exercise of the redemption rights will be adjusted upon the occurrence of stock splits, mergers, consolidations or similar pro-rata share transactions, which otherwise would have the effect of diluting the ownership interests of the limited partners or our stockholders. As of December 31, 2011 and 2010, there were no operating partnership units held by unaffiliated third parties.

Capital Stock

Common Shares

We are authorized to issue up to 200,000,000 shares of common stock, $0.01 par value per share. Each outstanding share of common stock entitles the holder to one vote on all matters submitted to a vote of stockholders. Holders of our common stock are entitled to receive dividends out of assets legally available for the payment of dividends when authorized by our board of directors.

Follow-On Public Offerings. On January 31, 2011, we completed a follow-on public offering of our common stock. We sold 12,418,662 shares of our common stock, including the underwriter’s option to purchase 1,418,662 additional shares, at a public offering price of $12.15 per share. The net proceeds to us, after deduction of offering costs, were approximately $149.6 million. On May 28, 2010, we completed a follow-on public offering of our common stock. We sold 23,000,000 shares of common stock, including the underwriters' overallotment of 3,000,000 shares, at a public offering price of $8.40 per share. The net proceeds to us, after deduction of offering costs, were approximately $184.6 million.

Preferred Shares

We are authorized to issue up to 10,000,000 shares of preferred stock, $0.01 par value per share. Our board of directors is required to set for each class or series of preferred stock the terms, preferences, conversion or other rights, voting powers, restrictions, limitations as to dividends or other distributions, qualifications, and terms or conditions of redemption. As of December 31, 2011 and 2010, there were no shares of preferred stock outstanding.

Operating Partnership Units

Holders of operating partnership units have certain redemption rights, which enable them to cause our operating partnership to redeem their units in exchange for cash per unit equal to the market price of our common stock, at the time of redemption, or, at our option for shares of our common stock on a one-for-one basis. The number of shares issuable upon exercise of the redemption rights will be adjusted upon the occurrence of stock splits, mergers, consolidations or similar pro-rata share transactions, which otherwise would have the effect of diluting the ownership interests of the limited partners or our stockholders. As of December 31, 2011 and 2010, there were no operating partnership units held by unaffiliated third parties.