Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Consolidated Balance Sheets
Net of allowance on accounts receivable	$ 24,276	$ 22,379
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	70,000,000	70,000,000
Common stock, shares outstanding	31,898,868	31,941,441