Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets, Current [Abstract]
Allowance for uncollectible accounts	$ 16,546	$ 14,978
Liabilities and Equity [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	11,000	11,000
Preferred stock, shares outstanding	0	0
Stockholders' Equity Attributable to Parent [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	175,000	175,000
Common stock, shares outstanding	88,372	86,796