CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Patient accounts receivable, allowance for doubtful accounts	$ 20,994	$ 17,438
Property and equipment, accumulated depreciation	113,154	94,266
Intangible assets, accumulated amortization	$ 23,457	$ 20,611
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued
Preferred stock, outstanding
Common Stock, par value	$ 0.001	$ 0.001
Common Stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	31,876,508	30,328,549
Common stock, shares outstanding	31,086,619	29,639,735
Treasury Stock at cost, shares	789,889	688,814