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, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Other revenues	$ 101,274	$ 105,414
Total revenues	2,817,555	2,820,001
Operating income (loss)	338,308	442,602
Corporate administrative support	(35,827)	(25,444)
Debt expense	(73,791)	(67,014)
Other (loss) income, net	(1,786)	1,168
Income before income taxes	262,731	376,756
U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	2,552,927	2,562,875
Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	264,628	257,126
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	2,839,724	2,851,297
Operating income (loss)	374,135	468,046
Operating Segments | U.S. dialysis
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,569,120	2,583,203
Total revenues	2,575,096	2,589,878
Operating income (loss)	406,440	479,906
Operating Segments | U.S. dialysis | External Sources
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,546,961	2,556,259
Other revenues	5,966	6,616
Operating Segments | U.S. dialysis | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	22,159	26,944
Other revenues	10	59
Operating Segments | Other—Ancillary services
Segment Reporting Information [Line Items]
Dialysis patient service revenues	169,320	158,328
Other revenues	95,308	98,798
Total revenues	264,628	261,419
Operating income (loss)	(32,305)	(11,860)
Operating Segments | Other—Ancillary services | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues		4,293
Intersegment Elimination
Segment Reporting Information [Line Items]
Total revenues	(22,169)	(31,296)
Intersegment Elimination | U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	(22,169)	(27,003)
Intersegment Elimination | Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues		$ (4,293)