Equity (Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Realized investment gains (losses), net	$ (459)	$ 1,977	$ 432
Other income (loss)	3,262	(1,042)	1,301
Total Foreign Currency Translation Adjustment
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	27	1	1
Net Unrealized Investment Gains (Losses)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	(1,345)	(779)	(1,629)
Total amortization of defined benefit pension items
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	241	227	224
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	(1,077)	(551)	(1,404)
Amounts reclassified from AOCI
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Realized investment gains (losses), net	(27)	(1)	(3)
Other income (loss)	0	0	2
Amortization of defined benefit items:
Prior service cost	0	3	3
Actuarial gain (loss)	(241)	(230)	(227)
Amounts reclassified from AOCI | Total Foreign Currency Translation Adjustment
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	(27)	(1)	(1)
Amounts reclassified from AOCI | Net Unrealized Investment Gains (Losses)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	1,345	779	1,629
Amounts reclassified from AOCI | Total amortization of defined benefit pension items
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	(241)	(227)	(224)
Amounts reclassified from AOCI | Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	1,077	551	1,404
Amounts reclassified from AOCI | Net unrealized investment gains (losses) on available-for-sale securities
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net unrealized investment gains (losses)	966	228	1,647
Amounts reclassified from AOCI | Interest Rate | Cash Flow Hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net unrealized investment gains (losses)	58	1	(2)
Amounts reclassified from AOCI | Currency | Cash Flow Hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net unrealized investment gains (losses)	6	7	0
Amounts reclassified from AOCI | Currency/Interest Rate | Cash Flow Hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net unrealized investment gains (losses)	$ 315	$ 543	$ (16)