Goodwill - Changes in Goodwill by Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Sep. 30, 2018
Goodwill [Roll Forward]
Beginning balance			$ 6,610,279	$ 6,015,375	$ 6,015,375
Acquisitions			135,654		617,032
Divestitures			(15,497)		(32,386)
Goodwill impairment charges	$ 0	$ 0	(3,106)	(34,696)	(36,196)
Foreign currency and other adjustments			(24,671)		46,454
Ending balance	6,702,659		6,702,659		6,610,279
Goodwill						$ 6,730,260
Accumulated impairment charges						(27,601)
Total goodwill by reportable segments	6,702,659		6,610,279	6,015,375	6,015,375	6,702,659
U.S. dialysis and related lab services
Goodwill [Roll Forward]
Beginning balance			6,144,761	5,691,587	5,691,587
Acquisitions			24,431		485,434
Divestitures			(331)		(32,260)
Goodwill impairment charges			0		0
Foreign currency and other adjustments			0		0
Ending balance	6,168,861		6,168,861		6,144,761
Goodwill						6,168,861
Accumulated impairment charges						0
Total goodwill by reportable segments	6,168,861		6,144,761	5,691,587	5,691,587	6,168,861
Other—Ancillary services and strategic initiatives
Goodwill [Roll Forward]
Beginning balance			465,518	323,788	323,788
Acquisitions			111,223		131,598
Divestitures			(15,166)		(126)
Goodwill impairment charges			(3,106)		(36,196)
Foreign currency and other adjustments			(24,671)		46,454
Ending balance	533,798		533,798		465,518
Goodwill						561,399
Accumulated impairment charges						(27,601)
Total goodwill by reportable segments	$ 533,798		$ 465,518	$ 323,788	$ 323,788	$ 533,798