Organization and Significant Accounting Policies - Non-Controlling Interests and Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income (loss) attributable to non-controlling interests and redeemable non-controlling interests
Attributable to non-controlling interests	$ 7,822	$ (2,620)	$ 7,450
Attributable to redeemable non-controlling interests	35,639	12,479	(2,190)
Net income attributable to non-controlling interests	43,461	9,859	5,260
Non-controlling Interests
Net income (loss) attributable to non-controlling interests and redeemable non-controlling interests
Attributable to non-controlling interests	$ 7,822	$ (2,620)	$ 7,450
Net operating revenues \| Third-Party Payor Risk \| Medicare program
Revenue Recognition [Abstract]
Percentage of concentration risk	30.00%	30.00%	37.00%
Accounts receivable \| Third-Party Payor Risk \| Medicare program
Revenue Recognition [Abstract]
Percentage of concentration risk	27.00%	18.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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