Segment reporting - Summary of Assets by Segment (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Total assets	$ 17,046,672	$ 17,311,394
U.S. dialysis
ASSETS
Total assets	15,549,310	15,778,880
Other—Ancillary services
ASSETS
Total assets	$ 1,497,362	$ 1,532,514