Segment reporting - Summary of Assets by Segment (Phantom) (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Equity method and other investments	$ 254,499	$ 241,983
U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Equity method and other investments	130,144	124,188
Other—Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Equity method and other investments	$ 124,355	$ 117,795