INVESTMENTS - Fair Value of AFS Debt Securities by Contractual Maturity Date (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Fair value
Total fair value	$ 264,774	$ 288,522
Mortgage-backed securities
Amoritzed cost
Amortized cost, due within 1 year	165	188
Amortized cost, after 1 but within 5 years	229	211
Amortized cost, after 5 but within 10 years	430	523
Amortized cost, after 10 years	37,947	32,547
Amortized cost	38,771	33,469
Fair value
Fair value, due within 1 year	165	189
Fair value, after 1 but within 5 years	226	211
Fair value, after 5 but within 10 years	427	559
Fair value, after 10 years	36,413	32,662
Total fair value	37,231	33,621
U.S. Treasury and federal agency securities
Amoritzed cost
Amortized cost, due within 1 year	21,050	34,321
Amortized cost, after 1 but within 5 years	72,037	87,987
Amortized cost, after 5 but within 10 years	346	361
Amortized cost, after 10 years	0	0
Amortized cost	93,433	122,669
Fair value
Fair value, due within 1 year	21,009	34,448
Fair value, after 1 but within 5 years	69,191	87,633
Fair value, after 5 but within 10 years	325	359
Fair value, after 10 years	0	0
Total fair value	90,525	122,440
State and municipal
Amoritzed cost
Amortized cost, due within 1 year	29	40
Amortized cost, after 1 but within 5 years	109	121
Amortized cost, after 5 but within 10 years	229	156
Amortized cost, after 10 years	2,265	2,326
Amortized cost	2,632	2,643
Fair value
Fair value, due within 1 year	29	40
Fair value, after 1 but within 5 years	108	124
Fair value, after 5 but within 10 years	222	161
Fair value, after 10 years	2,145	2,296
Total fair value	2,504	2,621
Foreign government
Amoritzed cost
Amortized cost, due within 1 year	53,275	49,263
Amortized cost, after 1 but within 5 years	67,153	64,555
Amortized cost, after 5 but within 10 years	3,259	3,736
Amortized cost, after 10 years	1,592	1,872
Amortized cost	125,279	119,426
Fair value
Fair value, due within 1 year	53,145	49,223
Fair value, after 1 but within 5 years	65,622	63,961
Fair value, after 5 but within 10 years	3,090	3,656
Fair value, after 10 years	1,602	1,900
Total fair value	123,459	118,740
All other
Amoritzed cost
Amortized cost, due within 1 year	5,202	5,175
Amortized cost, after 1 but within 5 years	5,174	5,177
Amortized cost, after 5 but within 10 years	726	750
Amortized cost, after 10 years	53	54
Amortized cost	11,155	11,156
Fair value
Fair value, due within 1 year	5,191	5,180
Fair value, after 1 but within 5 years	5,166	5,149
Fair value, after 5 but within 10 years	684	750
Fair value, after 10 years	14	21
Total fair value	11,055	11,100
Debt securities AFS
Amoritzed cost
Amortized cost	271,270	289,363
Fair value
Total fair value	$ 264,774	$ 288,522