Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Accounts receivable, net of allowance	$ 3,336	$ 4,716
Stockholders’ equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	570,000	570,000
Common stock, issued (in shares)	197,080	193,469
Common stock, outstanding (in shares)	134,573	141,172
Treasury stock, at cost (in shares)	62,507	52,297