Acquisitions and divestitures - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($) clinic	Sep. 30, 2021 USD ($)
Business Acquisition [Line Items]
Cash paid to acquire businesses	$ 43,811	$ 45,143
Business Acquisition, Goodwill, Adjustment To Expected Tax Deductible Amount	34,769
Other current liabilities
Business Acquisition [Line Items]
Contingent earn-out obligations	9,461
Other long-term liabilities
Business Acquisition [Line Items]
Contingent earn-out obligations	16,310
Other companies
Business Acquisition [Line Items]
Contingent earn-out obligations	$ 25,771
Minimum | Other companies | EBITDA or Operating Income Performance Targets or Quality Margins
Business Acquisition [Line Items]
Earn-out consideration payment period	1 year
Maximum
Business Acquisition [Line Items]
Contingent earn-out obligations and liabilities assumed associated with acquisitions	$ 56,815
Maximum | Other companies | EBITDA or Operating Income Performance Targets or Quality Margins
Business Acquisition [Line Items]
Earn-out consideration payment period	5 years
Dialysis and other businesses
Business Acquisition [Line Items]
Cash paid to acquire businesses	$ 43,811
Contingent earn-out obligations and liabilities assumed associated with acquisitions	2,171
Deferred purchase price obligations	$ 11,726
US Dialysis | Dialysis and other businesses
Business Acquisition [Line Items]
Number of businesses acquired | clinic	5
Foreign Dialysis Centers | Dialysis and other businesses
Business Acquisition [Line Items]
Number of businesses acquired | clinic	8