Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Allowance for doubtful accounts	$ 3,317	$ 3,438
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	60,893,489	60,306,128
Treasury stock, at cost (in shares)	6,631,583	6,389,267