Summary of Assets by Segment (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Equity investments	$ 521,848	$ 502,389
U.S. dialysis and related lab services
Segment Reporting Information [Line Items]
Equity investments	85,769	66,924
DMG
Segment Reporting Information [Line Items]
Equity investments	12,579	10,350
Ancillary services and strategic initiatives
Segment Reporting Information [Line Items]
Equity investments	$ 423,500	$ 425,115

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant