INVESTMENTS - Fair Value of AFS Debt Securities by Contractual Maturity Date (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities, Debt Maturities
Total amortized cost	$ 299,125	$ 296,920
Total fair value	299,887	297,418
Mortgage-backed securities
Available-for-sale Securities, Debt Maturities
Due within 1 year, amortized cost	107	44
After 1 but within 5 years, amortized cost	1,544	931
After 5 but within 10 years, amortized cost	1,106	1,362
After 10 years, amortized cost	40,725	42,163
Total amortized cost	43,482	44,500
Fair value, due within 1 year	107	44
Fair value, after 1 but within 5 years	1,558	935
Fair value, after 5 but within 10 years	1,124	1,387
Fair value, after 10 years	41,160	42,642
Total fair value	43,949	45,008
U.S. Treasury and federal agency securities
Available-for-sale Securities, Debt Maturities
Due within 1 year, amortized cost	3,567	13,070
After 1 but within 5 years, amortized cost	110,883	104,982
After 5 but within 10 years, amortized cost	5,639	2,286
After 10 years, amortized cost	1,198	3,079
Total amortized cost	121,287	123,417
Fair value, due within 1 year	3,569	13,084
Fair value, after 1 but within 5 years	112,025	105,131
Fair value, after 5 but within 10 years	5,645	2,325
Fair value, after 10 years	1,133	3,150
Total fair value	122,372	123,690
State and municipal securities
Available-for-sale Securities, Debt Maturities
Due within 1 year, amortized cost	2,831	652
After 1 but within 5 years, amortized cost	1,986	4,387
After 5 but within 10 years, amortized cost	517	524
After 10 years, amortized cost	6,842	7,963
Total amortized cost	12,176	13,526
Fair value, due within 1 year	2,827	651
Fair value, after 1 but within 5 years	1,991	4,381
Fair value, after 5 but within 10 years	531	537
Fair value, after 10 years	6,047	7,130
Total fair value	11,396	12,699
Foreign government
Available-for-sale Securities, Debt Maturities
Due within 1 year, amortized cost	29,610	31,355
After 1 but within 5 years, amortized cost	46,168	41,913
After 5 but within 10 years, amortized cost	17,634	16,008
After 10 years, amortized cost	2,189	973
Total amortized cost	95,601	90,249
Fair value, due within 1 year	29,609	31,382
Fair value, after 1 but within 5 years	46,151	42,467
Fair value, after 5 but within 10 years	17,602	15,779
Fair value, after 10 years	2,243	1,069
Total fair value	95,605	90,697
All other
Available-for-sale Securities, Debt Maturities
Due within 1 year, amortized cost	2,154	1,248
After 1 but within 5 years, amortized cost	12,781	10,442
After 5 but within 10 years, amortized cost	7,870	7,282
After 10 years, amortized cost	3,774	6,256
Total amortized cost	26,579	25,228
Fair value, due within 1 year	2,154	1,251
Fair value, after 1 but within 5 years	12,856	10,535
Fair value, after 5 but within 10 years	7,839	7,318
Fair value, after 10 years	3,716	6,220
Total fair value	$ 26,565	$ 25,324