Shareholders' Equity And Dividend Restrictions (Change In AOCI Includes Changes In Unrealized Gains And Losses On Investments And Pension Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income, Before Tax
OCI	$ 928	$ 537	$ (618)
Pension obligations OCI	14	16	(6)
Accumulated Other Comprehensive Income, Income Tax
OCI	325	188	(218)
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	1,693
AOCI, balance at the end of the period	2,788	1,693
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	2,625	2,094	2,719
OCI before realized gains recognized in net income	1,054	653	(556)
Realized gains recognized in net income	(139)	(122)	(69)
OCI	915	531	(625)
AOCI, balance at the end of the period	3,540	2,625	2,094
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	908	722	942
OCI before realized gains recognized in net income	366	229	(196)
Realized gains recognized in net income	(49)	(43)	(24)
OCI	317	186	(220)
AOCI, balance at the end of the period	733	908	722
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	1,717	1,372	1,777
OCI before realized gains recognized in net income	688	424	(360)
Realized gains recognized in net income	(90)	(79)	(45)
OCI	598	345	(405)
AOCI, balance at the end of the period	2,807	1,717	1,372
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	(26)	(42)	(36)
OCI before realized gains recognized in net income	12	13	(12)
Realized gains recognized in net income	2	3	6
OCI	14	16	(6)
AOCI, balance at the end of the period	(12)	(26)	(42)
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	(8)	(14)	(12)
OCI before realized gains recognized in net income	6	5	(5)
Realized gains recognized in net income	1	1	3
OCI	7	6	(2)
AOCI, balance at the end of the period	(1)	(8)	(14)
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	(18)	(28)	(24)
OCI before realized gains recognized in net income	6	8	(7)
Realized gains recognized in net income	1	2	3
OCI	7	10	(4)
AOCI, balance at the end of the period	(11)	(18)	(28)
Accumulated Net Unrealized Gain (Loss) on Deferred Costs, Reserves And Other
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	(9)	1	(12)
OCI before realized gains recognized in net income	8	(8)	14
Realized gains recognized in net income	(9)	(2)	(1)
OCI	(1)	(10)	13
AOCI, balance at the end of the period	(10)	(9)	1
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	(3)	1	(3)
OCI before realized gains recognized in net income	5	(3)	5
Realized gains recognized in net income	(4)	(1)	(1)
OCI	1	(4)	4
AOCI, balance at the end of the period	(2)	(3)	1
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	(6)	0	(9)
OCI before realized gains recognized in net income	3	(5)	9
Realized gains recognized in net income	(5)	(1)	0
OCI	(2)	(6)	9
AOCI, balance at the end of the period	(8)	(6)	0
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income, Before Tax
AOCI, balance at the beginning of the period	2,590	2,053	2,671
Investments OCI	915	531	(625)
Pension obligations OCI	14	16	(6)
Life deferred acquisition costs, life policy reserves and other OCI	(1)	(10)	13
Total OCI	928	537	(618)
AOCI, balance at the end of the period	3,518	2,590	2,053
Accumulated Other Comprehensive Income, Income Tax
AOCI, balance at the beginning of the period	897	709	927
Investments OCI	317	186	(220)
Pension obligations OCI	7	6	(2)
Life deferred acquisition costs, life policy reserves and other OCI	1	(4)	4
Total OCI	325	188	(218)
AOCI, balance at the end of the period	730	897	709
Accumulated Other Comprehensive Income, Net of Tax
AOCI, balance at the beginning of the period	1,693	1,344	1,744
Investments OCI	598	345	(405)
Pension obligations OCI	7	10	(4)
Life deferred acquisition costs, life policy reserves and other OCI	(2)	(6)	9
Total OCI	603	349	(400)
AOCI, balance at the end of the period	2,788	1,693	1,344
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02 | Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income, Before Tax
Adjustment to reclassify certain tax effects from AOCI	0
Accumulated Other Comprehensive Income, Income Tax
Adjustment to reclassify certain tax effects from AOCI	(492)
Accumulated Other Comprehensive Income, Net of Tax
Adjustment to reclassify certain tax effects from AOCI	492
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2018-02 | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income, Before Tax
Adjustment to reclassify certain tax effects from AOCI	0
Accumulated Other Comprehensive Income, Income Tax
Adjustment to reclassify certain tax effects from AOCI	(492)
Accumulated Other Comprehensive Income, Net of Tax
Adjustment to reclassify certain tax effects from AOCI	$ 492	$ 0	$ 0