Liability for Policy and Contract Claims - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Long-term Care Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred related to insured events of prior year	$ (255)	$ (206)
Increase decrease in reserves for liability for policy and contract claims	37
U.S. Mortgage Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Increase decrease in reserves for liability for policy and contract claims	28
Policy Contract
Liability for Claims and Claims Adjustment Expense [Line Items]
Increase decrease in reserves for liability for policy and contract claims	$ 322