Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, share authorized	150,000,000	150,000,000
Common stock, share issued	89,655,124	89,315,767
Common stock, share outstanding	89,655,124	89,315,767