Acquisition of Tokio Millennium Re (Taxation) (Details) - TMR Group Entities $ in Millions	Mar. 22, 2019 USD ($)
Business Acquisition [Line Items]
Other assets - net deferred tax liability related to fair value adjustments and value of business acquired	$ 5.7
Deferred tax assets, valuation allowance	$ 35.7

Amount of deferred tax liability attributable to taxable temporary differences assumed at the acquisition date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116821951&loc=d3e31917-109318

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472

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