Contingencies - Performance Bonds (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Malpractice loss contingency, letters of credit and surety bonds	$ 16,097	$ 16,003

Amount of letters of credit and other surety bonds that are available for the future payment of malpractice claims.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 450
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6491354&loc=d3e6049-115624

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