Other Comprehensive Income and Accumulated Other Comprehensive Income (details) - Reclassifications - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains on the income statement	[1]	$ (19)	$ (10)	$ (10)	$ (20)
Reclassification adjustment impacting general and administrative expense on the income statement		1,054	1,032	2,049	2,027
Total reclassifications		(887)	(1,076)	(1,804)	(2,224)
Income tax (expense) benefit		(223)	(264)	(449)	(579)
Amounts reclassified from accumulated other comprehensive income, net of taxes		(664)	(812)	(1,355)	(1,645)
Accumulated Other Comprehensive Income (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Total reclassifications		(8)	9	8	14
Income tax (expense) benefit		(2)	3	3	5
Amounts reclassified from accumulated other comprehensive income, net of taxes		(6)	6	5	9
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains on the income statement		(24)	(17)	(35)	(35)
Income tax (expense) benefit		(8)	(6)	(12)	(12)
Amounts reclassified from accumulated other comprehensive income, net of taxes		(16)	(11)	(23)	(23)
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains on the income statement		1	2	12	2
Income tax (expense) benefit				4
Amounts reclassified from accumulated other comprehensive income, net of taxes		1	2	8	2
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting general and administrative expense on the income statement		15	24	31	47
Income tax (expense) benefit		6	9	11	17
Amounts reclassified from accumulated other comprehensive income, net of taxes		$ 9	$ 15	$ 20	$ 30

[1] Total other-than-temporary impairment (OTTI) losses were $(4) million and $(8) million for the three months ended June 30, 2016 and 2015, respectively, and $(32) million and $(12) million for the six months ended June 30, 2016 and 2015, respectively. Of total OTTI, credit losses of $(4) million and $(6) million for the three months ended June 30, 2016 and 2015, respectively, and $(22) million and $(9) million for the six months ended June 30, 2016 and 2015, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million and $(2) million for the three months ended June 30, 2016 and 2015, respectively, and $(10) million and $(3) million for the six months ended June 30, 2016 and 2015, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income.