Reserve for Unpaid Losses and Loss Adjustment Expenses - PC Additional Information (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended	63 Months Ended
	May 23, 2019	Mar. 31, 2022	Dec. 31, 2016	Mar. 31, 2022	Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Liability for Claims and Claims Adjustment Expense		$ 39,759		$ 39,759	$ 39,659
Reinsurance Recoverables, Gross		6,725		6,725	$ 6,622
Abuse Claims | General Liability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Liability for Claims and Claims Adjustment Expense		787		787
Adverse Development Cover Navigators Group [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Payments for Reinsurance	$ 91
Change in Deferred Gain on Retroactive Reinsurance		209		209
Reinsurance Recoverables, Gross		300		300
Adverse Development Cover Navigators Group [Member] | Retention Layer for Reserve for the Covered Liabilities as of the Inception Date [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Reinsurance Retention Policy, Amount Retained		1,816
Adverse Development Cover Navigators Group [Member] | Retention Layer Above Reserve for the Covered Liabilities as of the Inception Date [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Reinsurance Retention Policy, Amount Retained		100
Asbestos and Environmental
Liability for Claims and Claims Adjustment Expense [Line Items]
Payments for Reinsurance			$ 650
Reinsurance Retention Policy, Amount Retained			$ 1,700
Asbestos and Environmental | Asbestos and Environmental
Liability for Claims and Claims Adjustment Expense [Line Items]
Policyholder Benefits and Claims Incurred, Assumed				1,015
Change in Deferred Gain on Retroactive Reinsurance		365		$ 365
Asbestos and Environmental | Remaining [Member] | Asbestos and Environmental
Liability for Claims and Claims Adjustment Expense [Line Items]
Maximum adverse loss development to be ceded under agreement		485
Maximum | Adverse Development Cover Navigators Group [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Maximum adverse loss development to be ceded under agreement		300
Maximum | Asbestos and Environmental
Liability for Claims and Claims Adjustment Expense [Line Items]
Maximum adverse loss development to be ceded under agreement		$ 1,500