Summary of Significant Accounting Policies Variable Interest Entity (Details) $ in Millions	9 Months Ended
Sep. 30, 2017 USD ($)
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Credit Agreement Capacity	$ 8.5

The amount of activity, consisting of a transaction or a measure not described elsewhere in the taxonomy, occurring during the period between the reporting entity and the Variable Interest Entity (VIE) or potential VIE.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph d
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5747-111685

Name:	us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityOtherMeasureOfActivityAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration