Income Taxes (Income Taxes - Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Deferred tax assets related to state net operating loss carryforwards	$ 9	$ 7
State net operating loss carryforwards specific valuation allowances	$ 17	25
State net operating loss carryforwards expiration date	Dec. 31, 2038
Accrued interest liabilities, net of the related tax benefits	$ 4	3
Allocation of earnings for bad debt deductions of former thrift subsidiaries included in retained earnings	157	157
Interest expense recognized in connection with income taxes	$ 1	$ 1	$ 2
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount			$ 253