Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Condensed Consolidated Balance Sheets [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01	$ 0.01
Preferred stock, authorized	5,000,000	5,000,000	5,000,000
Preferred stock, issued	0	0	0
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Common stock, authorized	300,000,000	300,000,000	300,000,000
Common stock, issued	37,068,904	37,068,904	37,068,904
Treasury stock, shares	12,934,377	10,969,425	8,999,196