Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Consolidated Balance Sheets
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	245,000,000	245,000,000
Common stock, shares issued	111,041,666	112,963,413
Common stock, shares outstanding	111,041,666	112,963,413