Segment reporting - Summary of Segment Net Revenues, Segment Operating Income (Loss) and Reconciliation of Segment Income to Consolidated Income Before Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Other revenues	$ 100,379	$ 142,416	$ 304,346	$ 392,154
Total revenues	2,938,319	2,924,066	8,674,830	8,645,282
Operating income (loss)	474,877	437,669	1,407,955	1,312,965
Corporate administrative support	(28,153)	(25,841)	(79,093)	(122,514)
Debt expense	(72,829)	(73,658)	(213,167)	(243,642)
Debt prepayment, refinancing and redemption charges	0	(86,074)	0	(89,022)
Other (loss) income, net	(7,590)	5,395	8,766	10,590
Income from continuing operations before income taxes	394,458	283,332	1,203,554	990,891
U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	2,675,942	2,656,902	7,893,839	7,880,798
Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	262,377	267,164	780,991	764,484
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	2,960,423	2,965,462	8,749,548	8,762,671
Operating income (loss)	503,030	463,510	1,487,048	1,435,479
Operating Segments | U.S. dialysis
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,691,830	2,676,810	7,944,955	7,954,939
Total revenues	2,698,046	2,694,219	7,964,263	7,985,785
Operating income (loss)	509,939	470,596	1,523,625	1,484,833
Operating Segments | U.S. dialysis | External Sources
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,669,823	2,639,761	7,874,759	7,850,828
Other revenues	6,119	17,141	19,080	29,970
Operating Segments | U.S. dialysis | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	22,007	37,049	70,196	104,111
Other revenues	97	268	228	876
Operating Segments | Other—Ancillary services
Segment Reporting Information [Line Items]
Dialysis patient service revenues	168,117	141,889	495,725	402,300
Other revenues	94,260	125,275	285,266	362,184
Total revenues	262,377	271,243	785,285	776,886
Operating income (loss)	(6,909)	(7,086)	(36,577)	(49,354)
Operating Segments | Other—Ancillary services | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	0	4,079	4,294	12,402
Intersegment Elimination
Segment Reporting Information [Line Items]
Total revenues	(22,104)	(41,396)	(74,718)	(117,389)
Intersegment Elimination | U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	(22,104)	(37,317)	(70,424)	(104,987)
Intersegment Elimination | Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	$ 0	$ (4,079)	$ (4,294)	$ (12,402)