Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Incurred Claims and Allocated Claim Adjustment Expenses - International Excluding Hardy (Details) - International Excluding Hardy [Member] $ in Millions	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)	Dec. 31, 2007 USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 484
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,342
Short-duration Insurance Contracts, Accident Year 2007 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	27,149
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 4
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 159	$ 160	$ 162	$ 164	$ 172	$ 181	$ 194	$ 213	$ 219	$ 204
Short-duration Insurance Contracts, Accident Year 2008 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,119
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 7
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 207	210	209	200	207	207	214	226	$ 223
Short-duration Insurance Contracts, Accident Year 2009 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	21,362
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 13
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 213	222	231	234	247	247	245	$ 249
Short-duration Insurance Contracts, Accident Year 2010 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	22,877
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 18
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 190	196	203	211	217	223	$ 226
Short-duration Insurance Contracts, Accident Year 2011 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,361
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 14
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 216	223	233	253	260	$ 259
Short-duration Insurance Contracts, Accident Year 2012 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	25,306
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 34
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 244	245	252	266	$ 259
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	23,999
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 56
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 256	275	282	$ 281
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	24,859
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 82
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 284	284	$ 269
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	22,873
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 107
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 297	$ 282
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Number of Reported Claims per Million of Net Earned Premium	15,564
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 149
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 276