Other commitments - additional information (Detail) $ in Thousands	Mar. 31, 2019 USD ($)
Commitments to provide operating capital
Other Commitments [Line Items]
Other potential commitments to provide operating capital to several dialysis centers	$ 7,339

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant