Other Comprehensive Income, Cumulative OCI Balances (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
Cumulative OCI balances [Abstract]
Balance, beginning of period	$ 198,733	$ 205,910	$ 197,066	$ 208,079
Balance, beginning of period adjusted balance						$ 197,055	$ 208,055
Other comprehensive income (loss), net of tax	1,458	(541)	3,631	(3,200)
Less: Other comprehensive income (loss) from noncontrolling interests	0	1	0	1
Balance, end of period	200,037	206,069	200,037	206,069
Accounting Standards Update 2017-08 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Transition Adjustment					$ (111)
Cumulative other comprehensive income [Member]
Cumulative OCI balances [Abstract]
Balance, beginning of period	(3,682)	(4,921)	(6,336)	(2,144)
Balance, beginning of period adjusted balance						(5,855)	(2,262)
Net unrealized gains (losses) arising during the period	1,343	(658)	3,490	(3,438)
Amounts reclassified from accumulated other comprehensive income	115	117	141	238
Other comprehensive income (loss), net of tax	1,458	(541)	3,631	(3,200)
Balance, end of period	(2,224)	(5,461)	(2,224)	(5,461)
Cumulative other comprehensive income [Member] | Accounting Standards Update 2017-08 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Transition Adjustment						481
Cumulative other comprehensive income [Member] | Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Transition Adjustment							(118)
Debt securities, parent [Member]
Cumulative OCI balances [Abstract]
Balance, beginning of period	(566)	(2,491)	(3,122)	171
Balance, beginning of period adjusted balance						(2,641)	53
Net unrealized gains (losses) arising during the period	1,287	(465)	3,423	(3,060)
Amounts reclassified from accumulated other comprehensive income	30	37	(31)	88
Other comprehensive income (loss), net of tax	1,317	(428)	3,392	(2,972)
Balance, end of period	751	(2,919)	751	(2,919)
Debt securities, parent [Member] | Accounting Standards Update 2017-08 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Transition Adjustment						481
Debt securities, parent [Member] | Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Transition Adjustment							(118)
Derivative and hedging activities, parent [Member]
Cumulative OCI balances [Abstract]
Balance, beginning of period	(651)	(555)	(685)	(418)
Balance, beginning of period adjusted balance						(685)	(418)
Net unrealized gains (losses) arising during the period	43	(113)	17	(295)
Amounts reclassified from accumulated other comprehensive income	59	58	119	103
Other comprehensive income (loss), net of tax	102	(55)	136	(192)
Balance, end of period	(549)	(610)	(549)	(610)
Defined benefit plans adjustments, parent [Member]
Cumulative OCI balances [Abstract]
Balance, beginning of period	(2,272)	(1,779)	(2,296)	(1,808)
Balance, beginning of period adjusted balance						(2,296)	(1,808)
Net unrealized gains (losses) arising during the period	0	0	(3)	4
Amounts reclassified from accumulated other comprehensive income	26	22	53	47
Other comprehensive income (loss), net of tax	26	22	50	51
Balance, end of period	(2,246)	(1,757)	(2,246)	(1,757)
Foreign currency translation adjustments, parent [Member]
Cumulative OCI balances [Abstract]
Balance, beginning of period	(193)	(96)	(233)	(89)
Balance, beginning of period adjusted balance						(233)	(89)
Net unrealized gains (losses) arising during the period	13	(80)	53	(87)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive income (loss), net of tax	13	(80)	53	(87)
Balance, end of period	(180)	(175)	(180)	(175)
Noncontrolling Interest [Member]
Cumulative OCI balances [Abstract]
Balance, beginning of period	901	958	900	1,143
Balance, beginning of period adjusted balance						$ 900	$ 1,143
Less: Other comprehensive income (loss) from noncontrolling interests	0	(1)	0	(1)
Balance, end of period	995	881	995	881
AOCI Attributable to Noncontrolling Interest [Member]
Cumulative OCI balances [Abstract]
Less: Other comprehensive income (loss) from noncontrolling interests	0	(1)	0	(1)
Debt securities, noncontrolling interest [Member]
Cumulative OCI balances [Abstract]
Less: Other comprehensive income (loss) from noncontrolling interests	0	0	0	0
Derivative and hedging activities, noncontrolling interest [Member]
Cumulative OCI balances [Abstract]
Less: Other comprehensive income (loss) from noncontrolling interests	0	0	0	0
Defined benefit plans adjustments, noncontrolling interest [Member]
Cumulative OCI balances [Abstract]
Less: Other comprehensive income (loss) from noncontrolling interests	0	0	0	0
Foreign currency translation adjustments, noncontrolling interest [Member]
Cumulative OCI balances [Abstract]
Less: Other comprehensive income (loss) from noncontrolling interests	$ 0	$ (1)	$ 0	$ (1)