Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 4,433	$ 4,539
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	180,000,000	180,000,000
Common stock, shares issued	56,658,529	56,048,135
Treasury stock, shares	9,790,192	9,740,054