Segment reporting - Summary of Expenditures for Property and Equipment by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Expenditures for property and equipment	$ 175,040	$ 241,534	$ 373,918	$ 473,977
U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Expenditures for property and equipment	149,264	197,051	319,812	388,458
Other—Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Expenditures for property and equipment	7,062	22,184	15,640	32,172
DMG held for sale
Segment Reporting Information [Line Items]
Expenditures for property and equipment	$ 18,714	$ 22,299	$ 38,466	$ 53,347