Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses (Schedule of Liability for Unpaid Claims and Claims Adjustment Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Liability for Claims and Claims Adjustment Expenses (Rollforward) [Abstract]
Liability for Claims and Claims Adjustment Expense	$ 149	$ 169
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments	108	108	$ 120
Liability for Unpaid Claims and Claims Adjustment Expense, Net	41	49
Supplemental Information for Property, Casualty Insurance Underwriters, Reserves for Unpaid Claims and Claims Adjustment Expense	332	345
Prior Year Claims and Claims Adjustment Expense	0	(3)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	332	342	293
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(309)	(320)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(32)	(30)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(341)	(350)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	32	41	49
Liability for Claims and Claims Adjustment Expense	$ 140	$ 149	$ 169