SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014 Securities	Dec. 31, 2013 Securities
Schedule of Available-for-sale Securities [Line Items]
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Issues	126	286
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 7,290	$ 13,529
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Loss	(64)	(193)
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Issues	63	26
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,637	510
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Loss	(85)	(39)
Securities Available-for-sale, Continuous Unrealized Loss Position, Number of Issues	189	312
Securities Available-for-sale, Continuous Unrealized Loss Position, Fair Value	8,927	14,039
Securities Available-for-sale, Continuous Unrealized Loss Position, Gross Unrealized Loss	(149)	(232)
U.S. Treasury
Schedule of Available-for-sale Securities [Line Items]
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Issues	0
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Loss	0
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Issues	0
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Loss	0
Securities Available-for-sale, Continuous Unrealized Loss Position, Number of Issues	0
Securities Available-for-sale, Continuous Unrealized Loss Position, Fair Value	0
Securities Available-for-sale, Continuous Unrealized Loss Position, Gross Unrealized Loss	0
State and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Issues	0	1
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	10
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Loss	0	(1)
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Issues	1	0
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	10	0
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Loss	0	0
Securities Available-for-sale, Continuous Unrealized Loss Position, Number of Issues	1	1
Securities Available-for-sale, Continuous Unrealized Loss Position, Fair Value	10	10
Securities Available-for-sale, Continuous Unrealized Loss Position, Gross Unrealized Loss	0	(1)
Federal agencies and U.S. government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Issues	121	263
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	7,178	12,067
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Loss	(63)	(158)
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Issues	45	7
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,213	20
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Loss	(51)	(2)
Securities Available-for-sale, Continuous Unrealized Loss Position, Number of Issues	166	270
Securities Available-for-sale, Continuous Unrealized Loss Position, Fair Value	8,391	12,087
Securities Available-for-sale, Continuous Unrealized Loss Position, Gross Unrealized Loss	(114)	(160)
Other/non-agency
Schedule of Available-for-sale Securities [Line Items]
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Issues	5	22
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	112	1,452
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Loss	(1)	(34)
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Issues	17	19
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	414	490
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Loss	(34)	(37)
Securities Available-for-sale, Continuous Unrealized Loss Position, Number of Issues	22	41
Securities Available-for-sale, Continuous Unrealized Loss Position, Fair Value	526	1,942
Securities Available-for-sale, Continuous Unrealized Loss Position, Gross Unrealized Loss	(35)	(71)
Total mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Issues	126	285
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	7,290	13,519
Securities Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Gross Unrealized Loss	(64)	(192)
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Issues	62	26
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,627	510
Securities Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Gross Unrealized Loss	(85)	(39)
Securities Available-for-sale, Continuous Unrealized Loss Position, Number of Issues	188	311
Securities Available-for-sale, Continuous Unrealized Loss Position, Fair Value	8,917	14,029
Securities Available-for-sale, Continuous Unrealized Loss Position, Gross Unrealized Loss	$ (149)	$ (231)