Shareholders' Equity Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Net unrealized securities gains, before tax [Abstract]
Net unrealized securities gains (losses) arising during the period, before tax	[1]	$ (552)	$ 53
Reclassification of net securities (gains) losses included in net income, before tax	[2]	(5)	(18)
Impact of DAC, DSIC, unearned revenue, benefit reserves and reinsurance recoverables, before tax		216	(26)
Net unrealized securities gains (losses), before tax		(341)	9
Net unrealized derivatives gains, before tax [Abstract]
Reclassification of net derivative (gains) losses included in net income, before tax		0	2	[2]
Net unrealized derivatives gains (losses), before tax		0	2
Defined benefit plans net gain (loss) arising during the period, before tax		0	7
Defined benefit plans, before tax		0	7
Foreign currency translation, before tax		37	11
Other, before tax		0	(1)
Total other comprehensive income (loss), before tax		(304)	28
Net unrealized securities gains (losses), tax impact [Abstract]
Net unrealized securities gains (losses) arising during the period, tax	[1]	123	(17)
Reclassification of net securities (gains) losses included in net income, tax	[2]	1	6
Impact of DAC, DSIC, unearned revenue, benefit reserves and reinsurance recoverables, tax		(45)	9
Net unrealized securities gains (losses), tax		(79)	2
Net unrealized derivatives losses, tax impact [Abstract]
Reclassification of net derivative (gains) losses included in net income, tax		0	(1)	[2]
Net unrealized derivatives gains (losses), tax		0	(1)
Defined benefit plans net gain (loss) arising during the period, tax		0	(2)
Defined benefit plans, tax		0	(2)
Foreign currency translation, tax		(8)	(4)
Other, tax		0	0
Total other comprehensive income (loss), tax		71	(9)
Net unrealized securities gains (losses), net of tax [Abstract]
Net unrealized securities gains (losses) arising during the period, net of tax	[1]	(429)	36
Reclassification of net securities (gains) losses included in net income, net of tax	[2]	(4)	(12)
Impact of DAC, DSIC, unearned revenue, benefit reserves and reinsurance recoverables, net of tax		171	(17)
Net unrealized securities gains (losses), net of tax		(262)	7
Net unrealized derivatives losses, net of tax [Abstract]
Reclassification of net derivative (gains) losses included in net income, net of tax		0	1	[2]
Net unrealized derivatives gains (losses), net of tax		0	1
Defined benefit plans net gain (loss) arising during the period, net of tax		0	5
Defined benefit plans, net of tax		0	5
Foreign currency translation adjustment		29	7
Other, net of tax		0	(1)
Total other comprehensive income (loss), net of tax		$ (233)	$ 19

[1] Includes other-than-temporary impairment losses on Available-for-Sale securities related to factors other than credit that were recognized in other comprehensive income (loss) during the period.

[2] Reclassification amounts are recorded in net investment income.