Stockholders' Equity - Summary of Authorized, Issued, and Outstanding Shares (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Stockholders' Equity Note [Abstract]
Preferred stock, par value per share	$ 0.01	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued	0	0	0
Preferred stock, shares outstanding	0	0	0
Common stock, par value per share	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000	400,000,000
Common stock, shares issued	296,860,119	296,564,382	296,150,999
Common stock, shares outstanding	296,860,119	296,564,382	296,150,999