Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets [Abstract]
Allowance for doubtful patient accounts	$ 2,201,875	$ 1,891,334
Accumulated amortization	$ 394,827	$ 313,028
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Common stock, par value per share	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	92,925,715	91,547,079
Common stock, shares outstanding	91,950,166	90,571,530
Treasury stock, shares	975,549	975,549