Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Allowance for uncollectible accounts	$ 14,978	$ 13,801
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	11,000	11,000
Preferred stock, shares outstanding
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	175,000	175,000
Common stock, shares outstanding	86,796	86,179