Reserve for Unpaid Losses and Loss Adjustment Expenses - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Unpaid losses and loss adjustment expenses	$ 39,659	$ 37,855
Group Benefits
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior accident year development [1]	(458)	(445)	$ (410)
Unpaid losses and loss adjustment expenses	8,210	8,233	8,256	$ 8,445
Group Benefits | Group long-term disability
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior accident year development [1]	380	365	340
Unpaid losses and loss adjustment expenses	6,671
Group Benefits | Group life and accident, excluding premium waiver
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior accident year development [1]	65	65	$ 60
Unpaid losses and loss adjustment expenses	833
Group Benefits | Group supplemental health
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior accident year development [1]	10	15
Unpaid losses and loss adjustment expenses	39
Liability | Abuse Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior accident year development [1]		$ 254
Unpaid losses and loss adjustment expenses	$ 787