Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense			$ 140	$ 149
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments			108	108
Liability for Unpaid Claims and Claims Adjustment Expense, Net			32	41
Current Year Claims and Claims Adjustment Expense			159	211
Prior Year Claims and Claims Adjustment Expense			5	2
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	$ 101	$ 125	164	213
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year			121	183
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years			26	27
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid			147	210
Liability for Unpaid Claims and Claims Adjustment Expense, Net	49	44	49	44
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments	100	135	100	135
Liability for Claims and Claims Adjustment Expense	$ 149	$ 179	$ 149	$ 179