Claim and Claim Adjustment Expense Reserves (International - Hardy - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - Hardy - International $ in Millions	Dec. 31, 2019 USD ($) claim	Dec. 31, 2018 USD ($)	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	$ 1,800
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented	461
IBNR	198
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	51	$ 51	$ 52	$ 53	$ 46	$ 52	$ 48	(10)
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented								39
IBNR	$ (1)
Cumulative Number of Claims | claim	4,565
2011
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Net Claim and Claim Adjustment Expense Reserves at Acquisition								126
Incurred claims and allocated claim adjustment expense, net	$ 142	142	139	139	140	136	136	(1)
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented								125
IBNR	$ (1)
Cumulative Number of Claims | claim	6,292
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	116	113	113	119	112	105	71
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented								$ 104
IBNR	$ 1
Cumulative Number of Claims | claim	6,950
2013
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 145	144	141	140	138	146	$ 131
IBNR	$ 2
Cumulative Number of Claims | claim	7,724
2014
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 172	171	171	177	183	$ 185
IBNR	$ 0
Cumulative Number of Claims | claim	8,242
2015
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 178	179	179	180	$ 191
IBNR	$ 1
Cumulative Number of Claims | claim	9,274
2016
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 225	236	247	$ 229
IBNR	$ 18
Cumulative Number of Claims | claim	10,152
2017
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 244	255	$ 245
IBNR	$ 15
Cumulative Number of Claims | claim	11,837
2018
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 305	$ 273
IBNR	$ 43
Cumulative Number of Claims | claim	12,646
2019
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 223
IBNR	$ 120
Cumulative Number of Claims | claim	6,271