Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses (Rollforward of Reserves for Insurance Losses and Loss Adjustment Expenses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves for insurance losses and loss adjustment expenses	$ 122	$ 134
Reinsurance recoverable	88	96
Net reserves for insurance losses and loss adjustment expenses	34	38
Net insurance losses and loss adjustment expenses, current year	72	59
Net insurance losses and loss adjustment expenses, prior years	2	0
Net insurance losses and loss adjustment expenses incurred	74	59
Net insurance losses and loss adjustment expenses paid or payable, current year	(46)	(33)
Net insurance losses and loss adjustment expenses paid or payable, prior years	(24)	(23)
Total net insurance losses and loss adjustment expenses paid or payable	(70)	(56)
Net reserves for insurance losses and loss adjustment expenses	38	41
Reinsurance recoverable	104	94
Gross reserves for insurance losses and loss adjustment expenses	$ 142	$ 135