Redeemable Noncontrolling Interests - Narrative (Details)	9 Months Ended
Sep. 30, 2018
Minimum
Noncontrolling Interest [Line Items]
Exercise period	4 years
Maximum
Noncontrolling Interest [Line Items]
Exercise period	7 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.

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