Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	46,410,007	46,410,007
Common stock, shares outstanding (in shares)	43,283,602	43,075,410
Treasury stock, at cost (in shares)	3,126,405	3,334,597