Summary of Significant Accounting Policies Unearned Premiums (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Unearned premiums	$ 2,397.1	$ 2,224.7
General Insurance Group [Member]
Unearned premiums	2,396.7	2,223.4
RFIG Run-off Business [Member]
Unearned premiums	$ 0.4	$ 1.3

Carrying amount of premiums written on insurance contracts that have not been earned as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(13)(a)(2))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Name:	us-gaap_UnearnedPremiums
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant