Claim and Claim Adjustment Expense Reserves Short Duration Contracts - Net Cumulative Paid Claim and Claim Adjustment Expenses International Excluding Hardy (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	$ 4,167	$ 4,089	$ 4,355
Liability for Unpaid Claims and Claims Adjustment Expense, Net	18,249	18,576	18,927	$ 19,117
International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,521
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	821
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	38
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	22
Liability for Unpaid Claims and Claims Adjustment Expense, Net	881
Short-duration Insurance Contracts, Accident Year 2007 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	152	150	148	144	$ 140	$ 133	$ 124	$ 112	$ 99	$ 31
Short-duration Insurance Contracts, Accident Year 2008 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	190	172	165	151	143	135	126	84	$ 34
Short-duration Insurance Contracts, Accident Year 2009 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	181	170	159	149	134	119	90	$ 38
Short-duration Insurance Contracts, Accident Year 2010 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	160	151	143	130	115	93	$ 47
Short-duration Insurance Contracts, Accident Year 2011 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	171	159	146	133	111	$ 44
Short-duration Insurance Contracts, Accident Year 2012 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	176	161	142	109	$ 42
Short-duration Insurance Contracts, Accident Year 2013 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	152	135	109	$ 49
Short-duration Insurance Contracts, Accident Year 2014 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	145	119	$ 51
Short-duration Insurance Contracts, Accident Year 2015 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	130	$ 55
Short-duration Insurance Contracts, Accident Year 2016 [Member] | International Excluding Hardy [Member]
Short-Duration Insurance Contracts, Net Cumulative Paid Claim and Claim Adjustment Expenses [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 64