Subsequent Events Subsequent Events - Acqusition (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Subsequent Event [Line Items]
Subsequent Event, Date	Jan. 11, 2019
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 12

Date the event occurred after the balance sheet date but before financial statements are issues or available to be issued, in CCYY-MM-DD format.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 855
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6842918&loc=SL6314017-165662

Name:	us-gaap_SubsequentEventsDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration