Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Restricted cash (in dollars)	$ 0	$ 200
Restricted marketable securities, current (in dollars)	222	57
Accounts receivable reserve (in dollars)	4,632	3,807
Restricted marketable securities, noncurrent (in dollars)	$ 50	$ 43
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares designated as Series A Junior Participating Preferred Stock	700,000	700,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	700,000,000	700,000,000
Common stock, shares issued	202,712,865	200,199,536
Common stock, shares outstanding	178,115,006	177,782,814
Treasury stock, shares	24,597,859	22,416,722