Acquisitions and Divestitures - Additional Information (Details) $ in Thousands			3 Months Ended		12 Months Ended
	May 01, 2017 USD ($) patient state clinic outpatient_dialysis_center	Aug. 01, 2016 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) clinic	Dec. 31, 2017 USD ($) clinic	Dec. 31, 2016 USD ($) clinic
Business Acquisition [Line Items]
Cash paid to acquire business					$ 183,156	$ 803,879	$ 563,856
Contingent earn-out obligations associated with acquisitions					1,246
Non-cash gain on acquiring additional ownership in business acquisition			$ 28,152		28,152
Contingent earn-out obligations			11,210		11,210
Fair value of contingent earn-out consideration			2,608		2,608	6,388
Other Accrued Liabilities
Business Acquisition [Line Items]
Fair value of contingent earn-out consideration			431		431
Other long-term liabilities
Business Acquisition [Line Items]
Fair value of contingent earn-out consideration			2,177		2,177
Other companies
Business Acquisition [Line Items]
Fair value of contingent earn-out consideration			2,608		$ 2,608
Minimum | Other companies | EBITDA or Operating Income Performance Targets or Quality Margins
Business Acquisition [Line Items]
Earn-out consideration payment period					1 year
Maximum | Other companies | EBITDA or Operating Income Performance Targets or Quality Margins
Business Acquisition [Line Items]
Earn-out consideration payment period					5 years
Renal Ventures Limited, LLC
Business Acquisition [Line Items]
Cash paid to acquire business	$ 359,913
Amortizable intangible assets acquired, weighted-average estimated useful lives					5 years
Goodwill deductible for tax purposes associated with acquisitions			298,200		$ 298,200
Ownership interest percentage	100.00%
Number of dialysis clinic patients | patient	2,600
Number of states where dialysis centers are located | state	6
Proceeds from divestiture of business	$ 21,219
Business acquisition, transaction costs						11,950
Series of individually immaterial business acquisitions
Business Acquisition [Line Items]
Cash paid to acquire business					176,161	308,550	165,108
Contingent earn-out obligations associated with acquisitions					1,246	2,692	1,511
Liabilities assumed					$ 34,394	$ 23,748	$ 17,963
Amortizable intangible assets acquired, weighted-average estimated useful lives					6 years	7 years	7 years
Goodwill deductible for tax purposes associated with acquisitions			$ 165,013		$ 165,013	$ 237,363	$ 169,379
U S Dialysis And Related Lab Services | Series of individually immaterial business acquisitions
Business Acquisition [Line Items]
Number of businesses acquired | clinic					18	30	8
Foreign Dialysis Centers | Series of individually immaterial business acquisitions
Business Acquisition [Line Items]
Number of businesses acquired | clinic					28	68	21
Operating Dialysis Center
Business Acquisition [Line Items]
Number of businesses divested | outpatient_dialysis_center	3
Operating Dialysis Center | Renal Ventures Limited, LLC
Business Acquisition [Line Items]
Number of businesses acquired | clinic	36
Number of businesses divested | outpatient_dialysis_center	3
New Center Under Construction | Renal Ventures Limited, LLC
Business Acquisition [Line Items]
Number of businesses acquired | clinic	1
Number of businesses divested | outpatient_dialysis_center	1
Home Dialysis Clinic | Renal Ventures Limited, LLC
Business Acquisition [Line Items]
Number of businesses acquired | clinic	1
Khazanah And Mitsui | Asia-Pacific dialysis business
Business Acquisition [Line Items]
Non-cash non-taxable gain		$ (374,374)		$ (6,273)