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, 2023	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Other revenues	$ 169,382		$ 102,200	$ 391,731	$ 320,132
Total revenues	3,121,332		2,948,694	8,994,400	8,693,006
Operating income (loss)	495,939		311,787	1,212,875	1,082,810
Corporate administrative support	(41,294)		(24,417)	(99,745)	(91,217)
Debt expense	(98,080)		(99,680)	(302,361)	(256,057)
Debt extinguishment and modification costs	0	$ (7,962)	0	(7,962)	0
Other loss, net	(19,650)		(4,898)	(14,525)	(7,968)
Income before income taxes	378,209		207,209	888,027	818,785
U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	2,761,017		2,680,296	8,061,383	7,877,073
Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	360,315		268,398	933,017	815,933
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	3,147,853		2,971,651	9,066,105	8,757,522
Operating income (loss)	537,233		336,203	1,312,620	1,174,026
Operating Segments | U.S. dialysis
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,779,067		2,697,197	8,109,259	7,923,465
Total revenues	2,785,306		2,703,253	8,128,081	7,941,589
Operating income (loss)	509,135		351,474	1,330,992	1,230,715
Operating Segments | U.S. dialysis | External Sources
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,754,778		2,674,240	8,042,561	7,858,939
Other revenues	6,239		6,056	18,822	18,134
Operating Segments | U.S. dialysis | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	24,289		22,957	66,698	64,526
Other revenues	0		0	0	(10)
Operating Segments | Other—Ancillary services
Segment Reporting Information [Line Items]
Dialysis patient service revenues	197,172		172,254	560,108	513,935
Other revenues	163,143		96,144	372,909	301,998
Total revenues	362,547		268,398	938,024	815,933
Operating income (loss)	28,098		(15,271)	(18,372)	(56,689)
Operating Segments | Other—Ancillary services | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,232		0	5,007	0
Intersegment Elimination
Segment Reporting Information [Line Items]
Total revenues	(26,521)		(22,957)	(71,705)	(64,516)
Intersegment Elimination | U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	(24,289)		$ (22,957)	(66,698)	$ (64,516)
Intersegment Elimination | Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	$ (2,232)			$ (5,007)