Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Stockholders' equity:
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	60,000	60,000
Preferred stock, issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	150,000,000	150,000,000
Common stock, shares issued	79,815,000	79,666,000
Treasury stock, shares	11,034,000	11,037,000