Segment Information - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment			4
Fee income in Excess and Surplus Lines segment \| $	$ 2.3	$ 3.7	$ 5.0	$ 8.5

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration