Statutory Requirements - Statutory Maximum Dividends (Details) - Bermuda - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
AARe
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval	$ 1,216	$ 997
ACRA
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval	$ 59	$ 0

Amount of dividends that can be declared or paid without approval of regulatory agency.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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