CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Patient accounts receivable, allowance for doubtful accounts	$ 19,933	$ 17,716
Property and equipment, accumulated depreciation	148,301	138,650
Intangible assets, accumulated amortization	$ 29,932	$ 27,864
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common Stock, par value	$ 0.001	$ 0.001
Common Stock, shares authorized	60,000,000	60,000,000
Common Stock, shares issued	35,687,068	35,253,577
Common Stock, shares outstanding	33,913,558	33,597,215
Treasury Stock at cost, shares	1,773,510	1,656,362