Segment reporting - Summary of Assets by Segment (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
ASSETS
Total assets	$ 17,810,311	$ 16,988,516
U.S. dialysis
ASSETS
Total assets	16,084,542	15,344,647
Other—Ancillary services
ASSETS
Total assets	$ 1,725,769	$ 1,643,869