Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses - International - Hardy (Details) - Hardy [Member] $ in Millions	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,030
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	310
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	123
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	15	$ 10	$ 16	$ 11	$ 7
Net Claim and Claim Adjustment Expense Reserves at Acquisition					5
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					12
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	4,249
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 13	13	12	11	(4)
Net Claim and Claim Adjustment Expense Reserves at Acquisition					18
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					14
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	4,234
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ (2)	1	(4)	6	1
Net Claim and Claim Adjustment Expense Reserves at Acquisition					11
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					12
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	3,840
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 50	44	50	46	(10)
Net Claim and Claim Adjustment Expense Reserves at Acquisition					46
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					36
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	4,495
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 132	134	130	130	0
Net Claim and Claim Adjustment Expense Reserves at Acquisition					121
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					121
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (2)
Number of Reported Claims per Million of Net Earned Premium	6,193
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 110	117	110	102	69
Net Claim and Claim Adjustment Expense Reserves at Acquisition					33
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net					$ 102
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ (1)
Number of Reported Claims per Million of Net Earned Premium	6,758
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 137	136	144	$ 127
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Number of Reported Claims per Million of Net Earned Premium	7,392
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 174	180	$ 182
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 7
Number of Reported Claims per Million of Net Earned Premium	7,656
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 176	$ 187
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18
Number of Reported Claims per Million of Net Earned Premium	7,669
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 225
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 101
Number of Reported Claims per Million of Net Earned Premium	5,274