Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 17,695	$ 18,537	$ 19,175	$ 19,181
Other comprehensive income (loss) before reclassifications, after tax	(1,425)	341	(3,039)	(249)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	20	(15)	29	(36)
Other comprehensive income (loss)	(1,405)	326	(3,010)	(285)
Amounts attributable to noncontrolling interests	146	(33)	314	31
Balance at end of period	16,221	19,398	16,221	19,398
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	(6)	0	(2)	0
Other comprehensive income (loss) before reclassifications, after tax	(1)	1	(5)	(2)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	(1)	(1)	(1)	2
Other comprehensive income (loss)	(2)	0	(6)	0
Amounts attributable to noncontrolling interests	1		1
Balance at end of period	(7)	0	(7)	0
Other comprehensive income (loss) before reclassifications, tax	(1)	0	0	1
Reclassification from AOCI, current period, tax	1	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	(513)	1,002	930	1,563
Other comprehensive income (loss) before reclassifications, after tax	(1,360)	323	(2,972)	(270)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	14	(23)	15	(57)
Other comprehensive income (loss)	(1,346)	300	(2,957)	(327)
Amounts attributable to noncontrolling interests	138	(31)	306	35
Balance at end of period	(1,721)	1,271	(1,721)	1,271
Other comprehensive income (loss) before reclassifications, tax	359	(82)	784	72
Reclassification from AOCI, current period, tax	(3)	7	(4)	15
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	12	(19)	(6)	(23)
Other comprehensive income (loss) before reclassifications, after tax	6	8	21	11
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax			3	1
Other comprehensive income (loss)	6	8	24	12
Amounts attributable to noncontrolling interests
Balance at end of period	18	(11)	18	(11)
Other comprehensive income (loss) before reclassifications, tax	5	(1)	3	(3)
Reclassification from AOCI, current period, tax	2	(1)	1	(2)
Pension and Postretirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(630)	(869)	(636)	(877)
Other comprehensive income (loss) before reclassifications, after tax	(2)	(2)		(2)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	7	9	12	18
Other comprehensive income (loss)	5	7	12	16
Amounts attributable to noncontrolling interests		(1)	(1)	(2)
Balance at end of period	(625)	(863)	(625)	(863)
Other comprehensive income (loss) before reclassifications, tax	2	0	0	0
Reclassification from AOCI, current period, tax	(1)	(3)	(3)	(5)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(114)	(80)	(100)	(82)
Other comprehensive income (loss) before reclassifications, after tax	(68)	11	(83)	14
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax
Other comprehensive income (loss)	(68)	11	(83)	14
Amounts attributable to noncontrolling interests	7	(1)	8	(2)
Balance at end of period	(175)	(70)	(175)	(70)
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	(1,251)	34	186	581
Balance at end of period	$ (2,510)	$ 327	$ (2,510)	$ 327