Investments (Details) - Net Unrealized Investment Gains - USD ($) $ in Millions		12 Months Ended
Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains (losses)		$ 3,140	$ (1,819)	$ 522
Income tax expense (benefit)		641	(349)	110
Change in net unrealized gains (losses) on investment securities, net of tax		2,499	(1,470)	412
Balance, beginning of year		(1,859)
Balance, end of year		640	(1,859)
Total net unrealized gains on investment securities (after-tax)				1,110
Net unrealized gains on investment securities reported in accumulated other comprehensive income (after-tax)				954
Adjustment reported in retained earnings due to the enactment of the Tax Cuts and Jobs Act of 2017				158
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains (losses)		3,140	(1,819)	522
Income tax expense (benefit)		641	(349)	110
Change in net unrealized gains (losses) on investment securities, net of tax		2,499	(1,470)	412
Cumulative effect of adoption of updated accounting guidance for equity financial instruments	$ (22)			(22)
Reclassification of certain tax effects from adoption of updated accounting guidance	(24)		(24)
Changes in Net Unrealized Gains on Investment Securities [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains (losses)		2,990	(1,516)	302
Income tax expense (benefit)		631	(319)	78
Change in net unrealized gains (losses) on investment securities, net of tax		2,359	(1,197)	224
Cumulative effect of adoption of updated accounting guidance for equity financial instruments			(22)
Reclassification of certain tax effects from adoption of updated accounting guidance			152
Balance, beginning of year	$ 954	(113)	954	730
Balance, end of year		2,246	(113)	954
Changes in Net Unrealized Gains on Investment Securities [Member] \| Fixed maturities [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains (losses)		2,990	(1,515)	513
Changes in Net Unrealized Gains on Investment Securities [Member] \| Equity securities [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains (losses)		0	0	(215)
Changes in Net Unrealized Gains on Investment Securities [Member] \| Other investments [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains (losses)		$ 0	$ (1)	$ 4

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Net unrealized gains, net of tax, reported in accumulated other comprehensive income.

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Net unrealized gains, net of tax, included in shareholders’ equity.

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After-tax impact of the enactment of the Tax Cuts and Jobs Act of 2017 related to unrealized gains on investment securities that is included in Retained Earnings as a result of recognition in the Statement of Income.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Amount before tax of other comprehensive income (loss) attributable to parent entity.

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