Disposition of Metropolitan Property and Casualty Insurance Company - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) on Sale of Business		$ 363	$ 4,401
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		291	5,643
Metropolitan Property And Casualty Insurance Company
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Agreed upon proceeds from divestiture of business.				$ 3,900
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		$ 121	$ 115
Metropolitan Property And Casualty Insurance Company | Subsequent Event [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) on Sale of Business	$ 1,000