Segment reporting - Summary of Assets by Segment (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
ASSETS
Total assets	$ 16,928,740	$ 16,928,252
U.S. dialysis
ASSETS
Total assets	14,574,707	15,084,454
Other—Ancillary services
ASSETS
Total assets	$ 2,354,033	$ 1,843,798