Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets
Net of allowance on accounts receivable	$ 22,379,000	$ 18,844,000
Preferred stock, par value
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value
Common stock, shares authorized	70,000,000	70,000,000
Common stock, shares outstanding	31,941,441	31,283,772