Summary of Significant Accounting Policies - Percentage of Patient Accounts Receivable by Payor (Details) - Product Concentration Risk - Accounts Receivable	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Concentration risk percentage	100.00%	100.00%
Medicare
Concentration Risk [Line Items]
Concentration risk percentage	51.30%	60.80%
Medicaid
Concentration Risk [Line Items]
Concentration risk percentage	8.60%	5.80%
Managed Care, Commercial, and Other
Concentration Risk [Line Items]
Concentration risk percentage	40.10%	33.40%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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