Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Consolidated Balance Sheets
Net of allowance on accounts receivable	$ 26,537	$ 22,379
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	70,000	70,000
Common stock, shares outstanding	32,154	31,941