SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Mortgage Securitizations (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Cash Flows Between Transferor and Transferee
Gains recognized on the securitization			$ 0
U.S. government-sponsored agency guaranteed
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	$ 7,300,000,000	$ 6,100,000,000	12,900,000,000	$ 13,300,000,000
Contractual servicing fees received	100,000,000	100,000,000	200,000,000	300,000,000
Cash flows received on retained interests and other net cash flows	0	0	0	0
Gains recognized on the securitization	$ 48,000,000	$ 19,000,000	$ 90,000,000	$ 32,000,000
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Weighted average discount rate	7.00%	10.90%	7.00%	10.70%
Weighted average constant prepayment rate	9.30%	5.50%	13.60%	5.10%
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate			6.80%		8.40%
Weighted average constant prepayment rate			13.20%		15.30%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	$ 2,556,000,000		$ 2,556,000,000		$ 2,374,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(71,000,000)		(71,000,000)		(69,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(138,000,000)		(138,000,000)		(134,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(103,000,000)		(103,000,000)		(93,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	$ (199,000,000)		$ (199,000,000)		$ (179,000,000)
U.S. government-sponsored agency guaranteed | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate	0.00%	0.70%	0.00%	0.00%
Constant prepayment rate	5.70%	4.70%	5.70%	0.00%
Weighted average life	6 years 10 months 24 days	7 years 4 months 24 days	3 years 6 months
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate			0.00%		0.00%
Constant prepayment rate			6.10%		6.00%
Weighted average life			6 months
U.S. government-sponsored agency guaranteed | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate	8.20%	12.00%	8.20%	12.00%
Constant prepayment rate	15.50%	13.30%	34.90%	16.00%
Weighted average life	10 years 1 month 6 days	9 years 4 months 24 days	10 years 1 month 6 days	9 years 8 months 12 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate			22.80%		21.20%
Constant prepayment rate			28.60%		41.40%
Weighted average life			21 years 7 months 6 days		16 years
Mortgage securitizations - Non-agency-sponsored
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	$ 2,500,000,000	$ 3,600,000,000	$ 6,100,000,000	$ 5,200,000,000
Contractual servicing fees received	0	0	0	0
Cash flows received on retained interests and other net cash flows	0	0	0	0
Gains recognized on the securitization	$ 15,000,000	$ 25,000,000	$ 31,000,000	$ 29,000,000
Senior interests
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate	0.00%	4.60%	2.80%
Weighted average discount rate	0.00%	4.60%	2.80%	3.80%
Constant prepayment rate	0.00%	0.00%	0.00%	0.00%
Weighted average constant prepayment rate	0.00%	0.00%	0.00%	0.00%
Anticipated net credit losses	0.00%	40.00%	40.00%	40.00%
Weighted average anticipated net credit losses	0.00%	40.00%	40.00%	40.00%
Weighted average life		8 years 7 months 6 days	9 years 8 months 12 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate			10.80%		7.70%
Weighted average constant prepayment rate			13.80%		10.90%
Weighted average anticipated net credit losses			40.70%		51.70%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	$ 181,000,000		$ 181,000,000		$ 310,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(8,000,000)		(8,000,000)		(7,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(15,000,000)		(15,000,000)		(13,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(3,000,000)		(3,000,000)		(3,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(6,000,000)		(6,000,000)		(5,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(6,000,000)		(6,000,000)		(6,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	$ (12,000,000)		$ (12,000,000)		$ (10,000,000)
Senior interests | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate				1.40%
Weighted average life				2 years 7 months 6 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate			0.40%		1.10%
Constant prepayment rate			3.20%		2.00%
Anticipated net credit losses			0.00%		0.00%
Weighted average life			3 months 18 days		3 months 18 days
Senior interests | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate				4.60%
Weighted average life				8 years 7 months 6 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate			37.60%		47.10%
Constant prepayment rate			100.00%		100.00%
Anticipated net credit losses			83.00%		92.40%
Weighted average life			24 years 2 months 12 days		14 years 4 months 24 days
Subordinated interests
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Weighted average discount rate	11.60%	6.10%	5.50%	6.80%
Constant prepayment rate		3.30%
Weighted average constant prepayment rate	5.60%	3.30%	3.30%	5.20%
Anticipated net credit losses		58.50%
Weighted average anticipated net credit losses	45.70%	58.50%	40.20%	52.90%
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate			8.40%		8.20%
Weighted average constant prepayment rate			8.10%		7.20%
Weighted average anticipated net credit losses			49.80%		52.50%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	$ 547,000,000		$ 547,000,000		$ 554,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(29,000,000)		(29,000,000)		(30,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(56,000,000)		(56,000,000)		(57,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(10,000,000)		(10,000,000)		(9,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(20,000,000)		(20,000,000)		(18,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(9,000,000)		(9,000,000)		(9,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	$ (15,000,000)		$ (15,000,000)		$ (16,000,000)
Subordinated interests | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate	11.20%	2.60%	0.00%	2.60%
Constant prepayment rate	3.50%		0.00%	3.30%
Anticipated net credit losses	38.10%		0.00%	40.00%
Weighted average life	8 years 10 months 24 days	4 years		3 years
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate			1.50%		1.30%
Constant prepayment rate			0.50%		0.50%
Anticipated net credit losses			5.10%		13.70%
Weighted average life			4 months 24 days
Subordinated interests | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate	12.10%	7.00%	12.10%	9.10%
Constant prepayment rate	8.00%		8.00%	6.10%
Anticipated net credit losses	52.10%		55.90%	58.50%
Weighted average life	12 years 10 months 24 days	10 years 1 month 6 days	12 years 10 months 24 days	14 years 6 months
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate			20.00%		19.60%
Constant prepayment rate			21.50%		16.20%
Anticipated net credit losses			79.90%		83.80%
Weighted average life			21 years 10 months 24 days		24 years 4 months 24 days
Asset-backed securities
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	$ 0	$ 0	$ 0	$ 500,000,000