Segment reporting - Summary of Expenditures for Property and Equipment by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Expenditures for property and equipment	$ 198,878	$ 232,443
U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Expenditures for property and equipment	170,548	191,406
Other—Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Expenditures for property and equipment	8,578	9,988
DMG held for sale
Segment Reporting Information [Line Items]
Expenditures for property and equipment	$ 19,752	$ 31,049