Income Taxes - Significant Portions of Deferred Tax Liabilities and Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets, Net of Valuation Allowance	$ 128	$ 151
Deferred tax assets:
Net operating loss and capital carryforward	764	742
Loss reserves	218	148
Deferred Tax Assets, Debentures	22	29
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation	9	7
Other	5	1
Sub total deferred tax assets	1,019	927
Valuation allowance	891	777
Insurance intangible	78	90
Variable interest entities	13	12
Investments	22	32
Unearned premiums and credit fees	32	42
Other	7	8
Deferred Tax Liabilities, Gross, Noncurrent	152	183
Deferred Tax Liabilities, Net	$ 24	$ 32