Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 16,221	$ 19,398	$ 19,175	$ 19,181
Other comprehensive income (loss) before reclassifications, after tax	(1,529)	(150)	(4,568)	(399)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	104	(3)	133	(39)
Other comprehensive loss	(1,425)	(153)	(4,435)	(438)
Amounts attributable to noncontrolling interests	132	17	446	48
Balance at end of period	14,653	19,130	14,653	19,130
Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(7)	0	(2)	0
Other comprehensive income (loss) before reclassifications, after tax			(5)	(2)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	(2)		(3)	2
Other comprehensive loss	(2)	0	(8)	0
Amounts attributable to noncontrolling interests	(1)
Balance at end of period	(10)	0	(10)	0
Other comprehensive income (loss) before reclassifications, tax	1	0	1	1
Reclassification from AOCI, current period, tax	0	0	1	(1)
Net Unrealized Gains (Losses) on Other Investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1,721)	1,271	930	1,563
Other comprehensive income (loss) before reclassifications, after tax	(1,429)	(121)	(4,401)	(391)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	102	(17)	117	(74)
Other comprehensive loss	(1,327)	(138)	(4,284)	(465)
Amounts attributable to noncontrolling interests	124	14	430	49
Balance at end of period	(2,924)	1,147	(2,924)	1,147
Other comprehensive income (loss) before reclassifications, tax	381	32	1,165	104
Reclassification from AOCI, current period, tax	(11)	5	(15)	20
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	18	(11)	(6)	(23)
Other comprehensive income (loss) before reclassifications, after tax	6	1	27	12
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	(2)	1	1	2
Other comprehensive loss	4	2	28	14
Amounts attributable to noncontrolling interests
Balance at end of period	22	(9)	22	(9)
Other comprehensive income (loss) before reclassifications, tax	0	0	3	(3)
Reclassification from AOCI, current period, tax	(1)	0	0	(2)
Pension and Postretirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(625)	(863)	(636)	(877)
Other comprehensive income (loss) before reclassifications, after tax		3		1
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	6	13	18	31
Other comprehensive loss	6	16	18	32
Amounts attributable to noncontrolling interests	(1)	(1)	(2)	(3)
Balance at end of period	(620)	(848)	(620)	(848)
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0
Reclassification from AOCI, current period, tax	(2)	(2)	(5)	(7)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(175)	(70)	(100)	(82)
Other comprehensive income (loss) before reclassifications, after tax	(106)	(33)	(189)	(19)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax
Other comprehensive loss	(106)	(33)	(189)	(19)
Amounts attributable to noncontrolling interests	10	4	18	2
Balance at end of period	(271)	(99)	(271)	(99)
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0
Reclassification from AOCI, current period, tax	0	0	0	0
Total Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(2,510)	327	186	581
Balance at end of period	$ (3,803)	$ 191	$ (3,803)	$ 191