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Related Party Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transactions
Imputed interest (gains) expenses of contingent payment arrangements	$ (15,500,000)	$ (3,900,000)	$ 40,300,000
Prior Owner | Non- controlling Interests
Related Party Transactions
Investment partnerships with prior owners		2,500,000
Prior Owner | Other Liabilities
Related Party Transactions
Investment partnerships with prior owners	61,200,000	67,800,000
Affiliated Entity
Related Party Transactions
Imputed interest (gains) expenses of contingent payment arrangements	6,600,000	(2,800,000)
Affiliated Entity | Other Liabilities
Related Party Transactions
Contingent liabilities arrangements to related parties	9,400,000	8,600,000
Payments associated with contingent liabilities arrangements to related parties	$ 6,800,000	$ 0

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- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

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Amount of cash outflow, not made soon after acquisition date of business combination, to settle contingent consideration liability exceeding amount recognized at acquisition date. Includes, but is not limited to, measurement period adjustment and less amount paid soon after acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (ee)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3367-108585

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