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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Other revenues	$ 142,416	$ 126,886	$ 392,154	$ 359,198
Total revenues	2,924,066	2,904,078	8,645,282	8,489,895
Operating income (loss)	437,669	378,336	1,312,965	1,180,729
Corporate administrative support	25,841	24,681	122,514	65,546
Debt expense	(73,658)	(88,589)	(243,642)	(351,774)
Debt prepayment, refinancing and redemption charges	(86,074)	(21,242)	(89,022)	(33,402)
Other income, net	5,395	5,280	10,590	17,863
Income from continuing operations before income taxes	283,332	273,785	990,891	813,416
U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	2,656,902	2,659,065	7,880,798	7,782,735
Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	267,164	245,013	764,484	707,160
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	2,965,462	2,939,923	8,762,671	8,593,454
Operating income (loss)	463,510	403,017	1,435,479	1,246,275
Operating Segments | U.S. dialysis
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,676,810	2,681,119	7,954,939	7,855,357
Total revenues	2,694,219	2,691,427	7,985,785	7,876,072
Operating income (loss)	470,596	500,742	1,484,833	1,416,680
Operating Segments | U.S. dialysis | External Sources
Segment Reporting Information [Line Items]
Dialysis patient service revenues	2,639,761	2,648,969	7,850,828	7,762,746
Other revenues	17,141	10,096	29,970	19,989
Operating Segments | U.S. dialysis | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	37,049	32,150	104,111	92,611
Other revenues	268	212	876	726
Operating Segments | Other—Ancillary services
Segment Reporting Information [Line Items]
Dialysis patient service revenues	141,889	128,223	402,300	367,951
Other revenues	125,275	116,790	362,184	339,209
Total revenues	271,243	248,496	776,886	717,382
Operating income (loss)	(7,086)	(97,725)	(49,354)	(170,405)
Operating Segments | Other—Ancillary services | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis patient service revenues	4,079	3,483	12,402	10,222
Intersegment Elimination
Segment Reporting Information [Line Items]
Total revenues	(41,396)	(35,845)	(117,389)	(103,559)
Intersegment Elimination | U.S. dialysis
Segment Reporting Information [Line Items]
Total revenues	(37,317)	(32,362)	(104,987)	(93,337)
Intersegment Elimination | Other—Ancillary services
Segment Reporting Information [Line Items]
Total revenues	$ (4,079)	$ (3,483)	$ (12,402)	$ (10,222)