Acquisitions - Pro Forma Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pro Forma
Pro forma results of operations
Net revenue	$ 1,267,401	$ 1,215,869	$ 3,864,155	$ 3,687,574
Net income	45,721	21,929	153,144	85,317
Net income attributable to the Company	$ 34,441	$ 17,011	$ 116,135	$ 69,237
Basic income per common share (in dollars per share)	$ 0.26	$ 0.13	$ 0.86	$ 0.52
Diluted income per common share (in dollars per share)	$ 0.26	$ 0.13	$ 0.86	$ 0.52
U.S. HealthWorks
Acquisition costs
U.S. HealthWorks acquisition costs			$ 2,900
U.S. HealthWorks \| Pro Forma
Acquisition costs
U.S. HealthWorks acquisition costs			$ (2,900)	$ 5,700

Business Acquisition, Pro Forma Net Income (Loss) Attributable To Parent

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Represents acquisition costs excluded from proforma results.

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No definition available.

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

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