Property And Equipment (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property, Plant and Equipment [Line Items]
Purchase of an office building	$ 18,500,000
Property and equipment includes medical and other equipment held under capital leases	125,721,000	98,956,000
Accumulated depreciation of property and equipment held under capital leases	65,191,000	56,182,000
Recorded depreciation expense	15,000,000	13,500,000	11,200,000
Medical And Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment includes medical and other equipment held under capital leases	1,600,000	1,000,000
Accumulated depreciation of property and equipment held under capital leases	$ 1,100,000	$ 800,000

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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- Definition

Gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

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