Revenue Recognition Revenue Recognition Narrative (Details) - Management Services Agreements (MSA)	9 Months Ended
Sep. 30, 2018
Minimum
Disaggregation of Revenue [Line Items]
Contract term	3 years
Maximum
Disaggregation of Revenue [Line Items]
Contract term	5 years

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration