Claim and Claim Adjustment Expense Reserves (International - Hardy - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - Hardy - International $ in Millions	Dec. 31, 2018 USD ($) claims	Dec. 31, 2017 USD ($)	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]
Incurred claims and allocated claim adjustment expense, net	$ 1,550
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented	456
IBNR	185
2009
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Net Claim and Claim Adjustment Expense Reserves at Acquisition							$ 11
Incurred claims and allocated claim adjustment expense, net	(3)	$ (3)	$ (2)	$ 1	$ (4)	$ 6	0
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented							12
IBNR	$ (2)
Cumulative Number of Claims | claims	3,856
2010
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Net Claim and Claim Adjustment Expense Reserves at Acquisition							48
Incurred claims and allocated claim adjustment expense, net	$ 50	51	52	46	52	47	(9)
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented							38
IBNR	$ 0
Cumulative Number of Claims | claims	4,540
2011
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Net Claim and Claim Adjustment Expense Reserves at Acquisition							125
Incurred claims and allocated claim adjustment expense, net	$ 140	137	137	138	134	134	(1)
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented							124
IBNR	$ (2)
Cumulative Number of Claims | claims	6,252
2012
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Net Claim and Claim Adjustment Expense Reserves at Acquisition							33
Incurred claims and allocated claim adjustment expense, net	$ 115	113	113	119	112	104	71
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented							$ 104
IBNR	$ 1
Cumulative Number of Claims | claims	6,900
2013
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 144	140	139	138	146	$ 130
IBNR	$ 4
Cumulative Number of Claims | claims	7,624
2014
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 170	170	176	182	$ 184
IBNR	$ 2
Cumulative Number of Claims | claims	8,097
2015
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 178	177	179	$ 190
IBNR	$ 3
Cumulative Number of Claims | claims	8,968
2016
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 234	245	$ 227
IBNR	$ 28
Cumulative Number of Claims | claims	9,536
2017
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 252	$ 244
IBNR	$ 48
Cumulative Number of Claims | claims	10,309
2018
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 270
IBNR	$ 103
Cumulative Number of Claims | claims	7,563