Acquisitions and Divestitures - Acquisitions (Details) $ in Thousands	Nov. 01, 2017 dialysis_center	Dec. 31, 2019 USD ($)	Oct. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill		$ 538,609	$ 576,082	$ 571,339		$ 573,145
Goodwill expected to be deductible for tax purposes		4,774				647
Acquisitions 2019
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Cash		6,590
Equity interests		4,655
Property and equipment		1,232
Noncompete agreements		660
Goodwill		9,108
Other assets		245
Total consideration paid		$ 11,245
Dialysis Center in California
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Property and equipment					$ 329
Other assets					59
Total consideration paid					$ 388
Acquisition 2017
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Property and equipment						737
Noncompete agreements						93
Goodwill						725
Total consideration paid						$ 1,555
Number of dialysis centers | dialysis_center	2