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
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Other revenues	$ 112,665	$ 101,274
Total revenues	2,872,699	2,817,555
Operating income (loss)	311,645	338,308
Corporate administrative support	(24,588)	(35,827)
Debt expense	(100,774)	(73,791)
Other income (loss), net	3,752	(1,786)
Income before income taxes	214,623	262,731
U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	2,590,113	2,552,927
Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	282,586	264,628
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	2,896,114	2,839,724
Operating income (loss)	336,233	374,135
Operating Segments | U.S. dialysis
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,605,980	2,569,120
Total revenues	2,612,160	2,575,096
Operating income (loss)	361,098	406,440
Operating Segments | U.S. dialysis | External Sources
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,583,933	2,546,961
Other revenues	6,180	5,966
Operating Segments | U.S. dialysis | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	22,047	22,159
Other revenues	0	10
Operating Segments | Other—Ancillary services
Segment Reporting Information [Line Items]
Dialysis patient service revenues	176,101	169,320
Other revenues	106,485	95,308
Total revenues	283,954	264,628
Operating income (loss)	(24,865)	(32,305)
Operating Segments | Other—Ancillary services | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	1,368	0
Intersegment Elimination
Segment Reporting Information [Line Items]
Total revenues	(23,415)	(22,169)
Intersegment Elimination | U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	(22,047)	(22,169)
Intersegment Elimination | Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	$ (1,368)