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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Dialysis and related lab patient service revenues	$ 2,781,169	$ 2,670,701	$ 8,150,386	$ 7,980,178
Provision for uncollectible accounts	(3,977)	(11,977)	(19,689)	(35,838)
Net U.S. dialysis and related lab services patient service revenues	2,777,192	2,658,724	8,130,697	7,944,340
Other revenues	126,886	188,606	359,198	639,387
Total revenues	2,904,078	2,847,330	8,489,895	8,583,727
Operating income (loss)	378,336	289,038	1,180,729	1,137,916
Corporate administrative support	(24,681)	(40,836)	(65,546)	(70,605)
Debt expense	(88,589)	(125,927)	(351,774)	(359,135)
Debt prepayment, refinancing and redemption charges	(21,242)	0	(33,402)	0
Other income, net	5,280	4,007	17,863	10,583
Income from continuing operations before income taxes	273,785	167,118	813,416	789,364
U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Total revenues	2,659,065	2,551,377	7,782,735	7,639,101
Other—Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Total revenues	245,013	295,953	707,160	944,626
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	2,939,923	2,881,115	8,593,454	8,675,418
Operating income (loss)	403,017	329,874	1,246,275	1,208,521
Operating Segments | U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Dialysis and related lab patient service revenues	2,685,096	2,584,769	7,875,046	7,725,187
Provision for uncollectible accounts	(3,977)	(12,900)	(19,689)	(37,108)
Net U.S. dialysis and related lab services patient service revenues	2,681,119	2,571,869	7,855,357	7,688,079
Total revenues	2,691,427	2,576,801	7,876,072	7,703,044
Operating income (loss)	500,742	390,006	1,416,680	1,272,828
Operating Segments | U.S. dialysis and related lab services | External Sources
Segment Reporting Information [Line Items]
Dialysis and related lab patient service revenues	2,652,946	2,559,345	7,782,435	7,661,244
Other revenues	10,096	4,932	19,989	14,965
Operating Segments | U.S. dialysis and related lab services | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis and related lab patient service revenues	32,150	25,424	92,611	63,943
Other revenues	212	0	726	0
Operating Segments | Other—Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Dialysis and related lab patient service revenues	128,223	112,279	367,951	320,204
Other revenues	116,790	183,674	339,209	624,422
Total revenues	248,496	304,314	717,382	972,374
Operating income (loss)	(97,725)	(60,132)	(170,405)	(64,307)
Operating Segments | Other—Ancillary services and strategic initiatives | Intersubsegment Eliminations
Segment Reporting Information [Line Items]
Dialysis and related lab patient service revenues	3,483	8,361	10,222	27,748
Intersegment Elimination
Segment Reporting Information [Line Items]
Total revenues	(35,845)	(33,785)	(103,559)	(91,691)
Intersegment Elimination | U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Total revenues	(32,362)	(25,424)	(93,337)	(63,943)
Intersegment Elimination | Other—Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Total revenues	$ (3,483)	$ (8,361)	$ (10,222)	$ (27,748)