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Related Party Transactions (Details) - USD ($) $ in Thousands			12 Months Ended
	Mar. 25, 2019	Apr. 20, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 26, 2016
RELATED PARTY TRANSACTIONS
Period of weighted average maturity, clinic loans			3 months 18 days
Weighted average interest rate, clinic loans			5.31%
Clinic loan guarantee			$ 478	$ 2,813
Percentage tax savings payable to pre-IPO stockholders						85.00%
Income tax receivable agreement liability		$ 23,400	3,451
Financial instrument fair value			3,000	3,700	$ 7,500
Accrued but unpaid obligations under tax receivable agreement			451
Payments made for the income tax receivable agreement			1,280	6,376
Due to relatd parties			$ 5,262
Sublease agreement
RELATED PARTY TRANSACTIONS
Weighted average interest rate, clinic loans			6.10%
Total amount of initial financing			$ 2,609
Due to relatd parties			2,609
Due from related parties, current			182
Due from related parties, noncurrent			2,427
Director \| Independent Contractor Agreement, ECG Ventures, Inc.
RELATED PARTY TRANSACTIONS
Expense related to agreement			$ 1,456
Related party transaction, notice period prior to termination	30 days
Related party transaction, amounts of transaction	$ 100
Executive \| Financing Transactions
RELATED PARTY TRANSACTIONS
Period of weighted average maturity, clinic loans			3 years 7 months 6 days
Weighted average interest rate, clinic loans			4.92%
Principal loan outstanding amount on joint venture			$ 2,320	4,065
Loan guarantee			501
Affiliated entity \| Software services agreement
RELATED PARTY TRANSACTIONS
Expense related to agreement			$ 322	318
Minimum
RELATED PARTY TRANSACTIONS
Interest rate			4.33%
Minimum \| Sublease agreement
RELATED PARTY TRANSACTIONS
Interest rate			6.00%
Minimum \| Executive \| Financing Transactions
RELATED PARTY TRANSACTIONS
Interest rate			4.33%
Maximum
RELATED PARTY TRANSACTIONS
Interest rate			8.08%
Maximum \| Sublease agreement
RELATED PARTY TRANSACTIONS
Interest rate			8.10%
Maximum \| Executive \| Financing Transactions
RELATED PARTY TRANSACTIONS
Interest rate			6.30%
Kinetic \| Executive \| Software services agreement
RELATED PARTY TRANSACTIONS
Ownership percentage			51.00%
Kinetic \| Spouse of executive \| Software services agreement
RELATED PARTY TRANSACTIONS
Ownership percentage			2.50%
Loans Payable
RELATED PARTY TRANSACTIONS
Carrying amount of debt			$ 866	$ 5,078
Tax Receivable Agreement Liability (included in Income tax receivable agreement payable)
RELATED PARTY TRANSACTIONS
Tax receivable agreement liability			$ 3,000