For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.4)
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- Definition

Amount of revenue recognized for providing services to patients, net of provisions for contractual allowances and discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 605
-Section 45
-Paragraph 1
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Amount of the provision for bad debts related to patient service revenue.

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-Name Accounting Standards Codification
-Topic 954
-SubTopic 605
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Significant Accounting Policies Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net service revenue	$ 291,054	$ 244,249
Provision for bad debts		$ 0
Allowance for uncollectible accounts			$ 0
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net service revenue	4,900
Allowance for uncollectible accounts	$ 26,000